diff options
Diffstat (limited to 'src/3rdparty/libpng/libpng.3')
| -rw-r--r-- | src/3rdparty/libpng/libpng.3 | 2334 |
1 files changed, 1869 insertions, 465 deletions
diff --git a/src/3rdparty/libpng/libpng.3 b/src/3rdparty/libpng/libpng.3 index 6b77fde..04518ca 100644 --- a/src/3rdparty/libpng/libpng.3 +++ b/src/3rdparty/libpng/libpng.3 @@ -1,6 +1,6 @@ -.TH LIBPNG 3 "January 3, 2010" +.TH LIBPNG 3 "July 7, 2011" .SH NAME -libpng \- Portable Network Graphics (PNG) Reference Library 1.4.0 +libpng \- Portable Network Graphics (PNG) Reference Library 1.5.4 .SH SYNOPSIS \fI\fB @@ -16,6 +16,14 @@ libpng \- Portable Network Graphics (PNG) Reference Library 1.4.0 \fI\fB +\fBvoid png_build_grayscale_palette (int \fP\fIbit_depth\fP\fB, png_colorp \fIpalette\fP\fB);\fP + +\fI\fB + +\fBpng_voidp png_calloc (png_structp \fP\fIpng_ptr\fP\fB, png_alloc_size_t \fIsize\fP\fB);\fP + +\fI\fB + \fBvoid png_chunk_benign_error (png_structp \fP\fIpng_ptr\fP\fB, png_const_charp \fIerror\fP\fB);\fP \fI\fB @@ -48,7 +56,7 @@ libpng \- Portable Network Graphics (PNG) Reference Library 1.4.0 \fI\fB -\fBpng_structp png_create_read_struct_2(png_const_charp \fP\fIuser_png_ver\fP\fB, png_voidp \fP\fIerror_ptr\fP\fB, png_error_ptr \fP\fIerror_fn\fP\fB, png_error_ptr \fP\fIwarn_fn\fP\fB, png_voidp \fP\fImem_ptr\fP\fB, png_malloc_ptr \fP\fImalloc_fn\fP\fB, png_free_ptr \fIfree_fn\fP\fB);\fP +\fBpng_structp png_create_read_struct_2 (png_const_charp \fP\fIuser_png_ver\fP\fB, png_voidp \fP\fIerror_ptr\fP\fB, png_error_ptr \fP\fIerror_fn\fP\fB, png_error_ptr \fP\fIwarn_fn\fP\fB, png_voidp \fP\fImem_ptr\fP\fB, png_malloc_ptr \fP\fImalloc_fn\fP\fB, png_free_ptr \fIfree_fn\fP\fB);\fP \fI\fB @@ -56,7 +64,11 @@ libpng \- Portable Network Graphics (PNG) Reference Library 1.4.0 \fI\fB -\fBpng_structp png_create_write_struct_2(png_const_charp \fP\fIuser_png_ver\fP\fB, png_voidp \fP\fIerror_ptr\fP\fB, png_error_ptr \fP\fIerror_fn\fP\fB, png_error_ptr \fP\fIwarn_fn\fP\fB, png_voidp \fP\fImem_ptr\fP\fB, png_malloc_ptr \fP\fImalloc_fn\fP\fB, png_free_ptr \fIfree_fn\fP\fB);\fP +\fBpng_structp png_create_write_struct_2 (png_const_charp \fP\fIuser_png_ver\fP\fB, png_voidp \fP\fIerror_ptr\fP\fB, png_error_ptr \fP\fIerror_fn\fP\fB, png_error_ptr \fP\fIwarn_fn\fP\fB, png_voidp \fP\fImem_ptr\fP\fB, png_malloc_ptr \fP\fImalloc_fn\fP\fB, png_free_ptr \fIfree_fn\fP\fB);\fP + +\fI\fB + +\fBvoid png_data_freer (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, int \fP\fIfreer\fP\fB, png_uint_32 \fImask)\fP\fB);\fP \fI\fB @@ -72,6 +84,10 @@ libpng \- Portable Network Graphics (PNG) Reference Library 1.4.0 \fI\fB +\fBvoid png_err (png_structp \fIpng_ptr\fP\fB);\fP + +\fI\fB + \fBvoid png_error (png_structp \fP\fIpng_ptr\fP\fB, png_const_charp \fIerror\fP\fB);\fP \fI\fB @@ -84,7 +100,7 @@ libpng \- Portable Network Graphics (PNG) Reference Library 1.4.0 \fI\fB -\fBvoid png_free_default(png_structp \fP\fIpng_ptr\fP\fB, png_voidp \fIptr\fP\fB);\fP +\fBvoid png_free_default (png_structp \fP\fIpng_ptr\fP\fB, png_voidp \fIptr\fP\fB);\fP \fI\fB @@ -92,75 +108,89 @@ libpng \- Portable Network Graphics (PNG) Reference Library 1.4.0 \fI\fB -\fBpng_byte png_get_bit_depth (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP +\fBpng_byte png_get_bit_depth (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP + +\fI\fB + +\fBpng_uint_32 png_get_bKGD (png_const_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_color_16p \fI*background\fP\fB);\fP + +\fI\fB + +\fBpng_byte png_get_channels (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP \fI\fB -\fBpng_uint_32 png_get_bKGD (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_color_16p \fI*background\fP\fB);\fP +\fBpng_uint_32 png_get_cHRM (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fP\fIinfo_ptr\fP\fB, double \fP\fI*white_x\fP\fB, double \fP\fI*white_y\fP\fB, double \fP\fI*red_x\fP\fB, double \fP\fI*red_y\fP\fB, double \fP\fI*green_x\fP\fB, double \fP\fI*green_y\fP\fB, double \fP\fI*blue_x\fP\fB, double \fI*blue_y\fP\fB);\fP \fI\fB -\fBpng_byte png_get_channels (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP +\fBpng_uint_32 png_get_cHRM_fixed (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fP\fIinfo_ptr\fP\fB, png_uint_32 \fP\fI*white_x\fP\fB, png_uint_32 \fP\fI*white_y\fP\fB, png_uint_32 \fP\fI*red_x\fP\fB, png_uint_32 \fP\fI*red_y\fP\fB, png_uint_32 \fP\fI*green_x\fP\fB, png_uint_32 \fP\fI*green_y\fP\fB, png_uint_32 \fP\fI*blue_x\fP\fB, png_uint_32 \fI*blue_y\fP\fB);\fP \fI\fB -\fBpng_uint_32 png_get_cHRM (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, double \fP\fI*white_x\fP\fB, double \fP\fI*white_y\fP\fB, double \fP\fI*red_x\fP\fB, double \fP\fI*red_y\fP\fB, double \fP\fI*green_x\fP\fB, double \fP\fI*green_y\fP\fB, double \fP\fI*blue_x\fP\fB, double \fI*blue_y\fP\fB);\fP +\fBpng_uint_32 png_get_chunk_cache_max (png_const_structp \fIpng_ptr\fP\fB);\fP \fI\fB -\fBpng_uint_32 png_get_cHRM_fixed (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_uint_32 \fP\fI*white_x\fP\fB, png_uint_32 \fP\fI*white_y\fP\fB, png_uint_32 \fP\fI*red_x\fP\fB, png_uint_32 \fP\fI*red_y\fP\fB, png_uint_32 \fP\fI*green_x\fP\fB, png_uint_32 \fP\fI*green_y\fP\fB, png_uint_32 \fP\fI*blue_x\fP\fB, png_uint_32 \fI*blue_y\fP\fB);\fP +\fI\fB + +\fBpng_alloc_size_t png_get_chunk_malloc_max (png_const_structp \fIpng_ptr\fP\fB);\fP + +\fI\fB + +\fBpng_byte png_get_color_type (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP \fI\fB -\fBpng_uint_32 png_get_chunk_cache_max (png_structp \fIpng_ptr\fP\fB);\fP +\fBpng_uint_32 png_get_compression_buffer_size (png_const_structp \fIpng_ptr\fP\fB);\fP \fI\fB -\fBpng_byte png_get_color_type (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP +\fBpng_byte png_get_compression_type (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP \fI\fB -\fBpng_uint_32 png_get_compression_buffer_size (png_structp \fIpng_ptr\fP\fB);\fP +\fBpng_byte png_get_copyright (png_const_structp \fIpng_ptr\fP\fB);\fP \fI\fB -\fBpng_byte png_get_compression_type (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP +\fBpng_uint_32 png_get_current_row_number \fI(png_const_structp\fP\fB);\fP \fI\fB -\fBpng_byte png_get_copyright (png_structp \fIpng_ptr\fP\fB);\fP +\fBpng_byte png_get_current_pass_number \fI(png_const_structp\fP\fB);\fP \fI\fB -\fBpng_voidp png_get_error_ptr (png_structp \fIpng_ptr\fP\fB);\fP +\fBpng_voidp png_get_error_ptr (png_const_structp \fIpng_ptr\fP\fB);\fP \fI\fB -\fBpng_byte png_get_filter_type (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP +\fBpng_byte png_get_filter_type (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP \fI\fB -\fBpng_uint_32 png_get_gAMA (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, double \fI*file_gamma\fP\fB);\fP +\fBpng_uint_32 png_get_gAMA (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fP\fIinfo_ptr\fP\fB, double \fI*file_gamma\fP\fB);\fP \fI\fB -\fBpng_uint_32 png_get_gAMA_fixed (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_uint_32 \fI*int_file_gamma\fP\fB);\fP +\fBpng_uint_32 png_get_gAMA_fixed (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fP\fIinfo_ptr\fP\fB, png_uint_32 \fI*int_file_gamma\fP\fB);\fP \fI\fB -\fBpng_byte png_get_header_ver (png_structp \fIpng_ptr\fP\fB);\fP +\fBpng_byte png_get_header_ver (png_const_structp \fIpng_ptr\fP\fB);\fP \fI\fB -\fBpng_byte png_get_header_version (png_structp \fIpng_ptr\fP\fB);\fP +\fBpng_byte png_get_header_version (png_const_structp \fIpng_ptr\fP\fB);\fP \fI\fB -\fBpng_uint_32 png_get_hIST (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_uint_16p \fI*hist\fP\fB);\fP +\fBpng_uint_32 png_get_hIST (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fP\fIinfo_ptr\fP\fB, png_uint_16p \fI*hist\fP\fB);\fP \fI\fB -\fBpng_uint_32 png_get_iCCP (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_charpp \fP\fIname\fP\fB, int \fP\fI*compression_type\fP\fB, png_charpp \fP\fIprofile\fP\fB, png_uint_32 \fI*proflen\fP\fB);\fP +\fBpng_uint_32 png_get_iCCP (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fP\fIinfo_ptr\fP\fB, png_charpp \fP\fIname\fP\fB, int \fP\fI*compression_type\fP\fB, png_bytepp \fP\fIprofile\fP\fB, png_uint_32 \fI*proflen\fP\fB);\fP \fI\fB @@ -168,11 +198,11 @@ libpng \- Portable Network Graphics (PNG) Reference Library 1.4.0 \fI\fB -\fBpng_uint_32 png_get_image_height (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP +\fBpng_uint_32 png_get_image_height (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP \fI\fB -\fBpng_uint_32 png_get_image_width (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP +\fBpng_uint_32 png_get_image_width (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP \fI\fB @@ -180,7 +210,15 @@ libpng \- Portable Network Graphics (PNG) Reference Library 1.4.0 \fI\fB -\fBpng_byte png_get_interlace_type (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP +\fBpng_byte png_get_interlace_type (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP + +\fI\fB + +\fBpng_const_bytep png_get_io_chunk_name (png_structp \fIpng_ptr\fP\fB);\fP + +\fI\fB + +\fBpng_uint_32 png_get_io_chunk_type (png_const_structp \fIpng_ptr\fP\fB);\fP \fI\fB @@ -188,77 +226,105 @@ libpng \- Portable Network Graphics (PNG) Reference Library 1.4.0 \fI\fB -\fBpng_byte png_get_libpng_ver (png_structp \fIpng_ptr\fP\fB);\fP +\fBpng_uint_32 png_get_io_state (png_structp \fIpng_ptr\fP\fB);\fP + +\fI\fB + +\fBpng_byte png_get_libpng_ver (png_const_structp \fIpng_ptr\fP\fB);\fP + +\fI\fB + +\fBpng_voidp png_get_mem_ptr (png_const_structp \fIpng_ptr\fP\fB);\fP + +\fI\fB + +\fBpng_uint_32 png_get_oFFs (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fP\fIinfo_ptr\fP\fB, png_uint_32 \fP\fI*offset_x\fP\fB, png_uint_32 \fP\fI*offset_y\fP\fB, int \fI*unit_type\fP\fB);\fP + +\fI\fB + +\fBpng_uint_32 png_get_pCAL (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fP\fIinfo_ptr\fP\fB, png_charp \fP\fI*purpose\fP\fB, png_int_32 \fP\fI*X0\fP\fB, png_int_32 \fP\fI*X1\fP\fB, int \fP\fI*type\fP\fB, int \fP\fI*nparams\fP\fB, png_charp \fP\fI*units\fP\fB, png_charpp \fI*params\fP\fB);\fP + +\fI\fB + +\fBpng_uint_32 png_get_pHYs (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fP\fIinfo_ptr\fP\fB, png_uint_32 \fP\fI*res_x\fP\fB, png_uint_32 \fP\fI*res_y\fP\fB, int \fI*unit_type\fP\fB);\fP + +\fI\fB + +\fBfloat png_get_pixel_aspect_ratio (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP \fI\fB -\fBpng_voidp png_get_mem_ptr(png_structp \fIpng_ptr\fP\fB);\fP +\fBpng_uint_32 png_get_pHYs_dpi (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fP\fIinfo_ptr\fP\fB, png_uint_32 \fP\fI*res_x\fP\fB, png_uint_32 \fP\fI*res_y\fP\fB, int \fI*unit_type\fP\fB);\fP \fI\fB -\fBpng_uint_32 png_get_oFFs (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_uint_32 \fP\fI*offset_x\fP\fB, png_uint_32 \fP\fI*offset_y\fP\fB, int \fI*unit_type\fP\fB);\fP +\fBpng_fixed_point png_get_pixel_aspect_ratio_fixed (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP \fI\fB -\fBpng_uint_32 png_get_pCAL (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_charp \fP\fI*purpose\fP\fB, png_int_32 \fP\fI*X0\fP\fB, png_int_32 \fP\fI*X1\fP\fB, int \fP\fI*type\fP\fB, int \fP\fI*nparams\fP\fB, png_charp \fP\fI*units\fP\fB, png_charpp \fI*params\fP\fB);\fP +\fBpng_uint_32 png_get_pixels_per_inch (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP \fI\fB -\fBpng_uint_32 png_get_pHYs (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_uint_32 \fP\fI*res_x\fP\fB, png_uint_32 \fP\fI*res_y\fP\fB, int \fI*unit_type\fP\fB);\fP +\fBpng_uint_32 png_get_pixels_per_meter (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP \fI\fB -\fBfloat png_get_pixel_aspect_ratio (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP +\fBpng_voidp png_get_progressive_ptr (png_const_structp \fIpng_ptr\fP\fB);\fP \fI\fB -\fBpng_uint_32 png_get_pixels_per_meter (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP +\fBpng_uint_32 png_get_PLTE (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fP\fIinfo_ptr\fP\fB, png_colorp \fP\fI*palette\fP\fB, int \fI*num_palette\fP\fB);\fP \fI\fB -\fBpng_voidp png_get_progressive_ptr (png_structp \fIpng_ptr\fP\fB);\fP +\fBpng_byte png_get_rgb_to_gray_status (png_const_structp \fIpng_ptr) + +\fBpng_uint_32 png_get_rowbytes (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP \fI\fB -\fBpng_uint_32 png_get_PLTE (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_colorp \fP\fI*palette\fP\fB, int \fI*num_palette\fP\fB);\fP +\fBpng_bytepp png_get_rows (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP \fI\fB -\fBpng_byte png_get_rgb_to_gray_status (png_structp \fIpng_ptr) +\fBpng_uint_32 png_get_sBIT (png_const_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_color_8p \fI*sig_bit\fP\fB);\fP + +\fI\fB -\fBpng_uint_32 png_get_rowbytes (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP +\fBvoid png_get_sCAL (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fP\fIinfo_ptr\fP\fB, int* \fP\fIunit\fP\fB, double* \fP\fIwidth\fP\fB, double* \fIheight\fP\fB);\fP \fI\fB -\fBpng_bytepp png_get_rows (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP +\fBvoid png_get_sCAL_fixed (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fP\fIinfo_ptr\fP\fB, int* \fP\fIunit\fP\fB, png_fixed_pointp \fP\fIwidth\fP\fB, png_fixed_pointp \fIheight\fP\fB);\fP \fI\fB -\fBpng_uint_32 png_get_sBIT (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_color_8p \fI*sig_bit\fP\fB);\fP +\fBvoid png_get_sCAL_s (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fP\fIinfo_ptr\fP\fB, int* \fP\fIunit\fP\fB, png_charpp \fP\fIwidth\fP\fB, png_charpp \fIheight\fP\fB);\fP \fI\fB -\fBpng_bytep png_get_signature (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP +\fBpng_bytep png_get_signature (png_const_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP \fI\fB -\fBpng_uint_32 png_get_sPLT (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_spalette_p \fI*splt_ptr\fP\fB);\fP +\fBpng_uint_32 png_get_sPLT (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fP\fIinfo_ptr\fP\fB, png_spalette_p \fI*splt_ptr\fP\fB);\fP \fI\fB -\fBpng_uint_32 png_get_sRGB (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, int \fI*intent\fP\fB);\fP +\fBpng_uint_32 png_get_sRGB (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fP\fIinfo_ptr\fP\fB, int \fI*file_srgb_intent\fP\fB);\fP \fI\fB -\fBpng_uint_32 png_get_text (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_textp \fP\fI*text_ptr\fP\fB, int \fI*num_text\fP\fB);\fP +\fBpng_uint_32 png_get_text (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fP\fIinfo_ptr\fP\fB, png_textp \fP\fI*text_ptr\fP\fB, int \fI*num_text\fP\fB);\fP \fI\fB -\fBpng_uint_32 png_get_tIME (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_timep \fI*mod_time\fP\fB);\fP +\fBpng_uint_32 png_get_tIME (png_const_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_timep \fI*mod_time\fP\fB);\fP \fI\fB -\fBpng_uint_32 png_get_tRNS (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_bytep \fP\fI*trans\fP\fB, int \fP\fI*num_trans\fP\fB, png_color_16p \fI*trans_color\fP\fB);\fP +\fBpng_uint_32 png_get_tRNS (png_const_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_bytep \fP\fI*trans_alpha\fP\fB, int \fP\fI*num_trans\fP\fB, png_color_16p \fI*trans_color\fP\fB);\fP \fI\fB @@ -268,7 +334,7 @@ libpng \- Portable Network Graphics (PNG) Reference Library 1.4.0 \fI\fB -\fBpng_uint_32 png_get_uint_31 (png_bytep \fIbuf\fP\fB);\fP +\fBpng_uint_32 png_get_uint_31 (png_structp \fP\fIpng_ptr\fP\fB, png_bytep \fIbuf\fP\fB);\fP \fI\fB @@ -278,51 +344,75 @@ libpng \- Portable Network Graphics (PNG) Reference Library 1.4.0 \fI\fB -\fBpng_uint_32 png_get_unknown_chunks (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_unknown_chunkpp \fIunknowns\fP\fB);\fP +\fBpng_uint_32 png_get_unknown_chunks (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fP\fIinfo_ptr\fP\fB, png_unknown_chunkpp \fIunknowns\fP\fB);\fP + +\fI\fB + +\fBpng_voidp png_get_user_chunk_ptr (png_const_structp \fIpng_ptr\fP\fB);\fP + +\fI\fB + +\fBpng_uint_32 png_get_user_height_max (png_const_structp \fIpng_ptr\fP\fB);\fP + +\fI\fB + +\fBpng_voidp png_get_user_transform_ptr (png_const_structp \fIpng_ptr\fP\fB);\fP + +\fI\fB + +\fBpng_uint_32 png_get_user_width_max (png_const_structp \fIpng_ptr\fP\fB);\fP + +\fI\fB + +\fBpng_uint_32 png_get_valid (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fP\fIinfo_ptr\fP\fB, png_uint_32 \fIflag\fP\fB);\fP + +\fI\fB + +\fBfloat png_get_x_offset_inches (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP \fI\fB -\fBpng_voidp png_get_user_chunk_ptr (png_structp \fIpng_ptr\fP\fB);\fP +\fBpng_fixed_point png_get_x_offset_inches_fixed (png_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP \fI\fB -\fBpng_uint_32 png_get_user_height_max( png_structp \fIpng_ptr\fP\fB);\fP +\fBpng_int_32 png_get_x_offset_microns (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP \fI\fB -\fBpng_voidp png_get_user_transform_ptr (png_structp \fIpng_ptr\fP\fB);\fP +\fBpng_int_32 png_get_x_offset_pixels (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP \fI\fB -\fBpng_uint_32 png_get_user_width_max (png_structp \fIpng_ptr\fP\fB);\fP +\fBpng_uint_32 png_get_x_pixels_per_inch (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP \fI\fB -\fBpng_uint_32 png_get_valid (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_uint_32 \fIflag\fP\fB);\fP +\fBpng_uint_32 png_get_x_pixels_per_meter (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP \fI\fB -\fBpng_int_32 png_get_x_offset_microns (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP +\fBfloat png_get_y_offset_inches (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP \fI\fB -\fBpng_int_32 png_get_x_offset_pixels (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP +\fBpng_fixed_point png_get_y_offset_inches_fixed (png_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP \fI\fB -\fBpng_uint_32 png_get_x_pixels_per_meter (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP +\fBpng_int_32 png_get_y_offset_microns (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP \fI\fB -\fBpng_int_32 png_get_y_offset_microns (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP +\fBpng_int_32 png_get_y_offset_pixels (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP \fI\fB -\fBpng_int_32 png_get_y_offset_pixels (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP +\fBpng_uint_32 png_get_y_pixels_per_inch (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP \fI\fB -\fBpng_uint_32 png_get_y_pixels_per_meter (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fIinfo_ptr\fP\fB);\fP +\fBpng_uint_32 png_get_y_pixels_per_meter (png_const_structp \fP\fIpng_ptr\fP\fB, png_const_infop \fIinfo_ptr\fP\fB);\fP \fI\fB @@ -330,23 +420,31 @@ libpng \- Portable Network Graphics (PNG) Reference Library 1.4.0 \fI\fB +\fBvoid png_info_init_3 (png_infopp \fP\fIinfo_ptr\fP\fB, png_size_t \fIpng_info_struct_size\fP\fB);\fP + +\fI\fB + \fBvoid png_init_io (png_structp \fP\fIpng_ptr\fP\fB, FILE \fI*fp\fP\fB);\fP \fI\fB +\fBvoid png_longjmp (png_structp \fP\fIpng_ptr\fP\fB, int \fIval\fP\fB);\fP + +\fI\fB + \fBpng_voidp png_malloc (png_structp \fP\fIpng_ptr\fP\fB, png_alloc_size_t \fIsize\fP\fB);\fP \fI\fB -\fBpng_voidp png_malloc_default(png_structp \fP\fIpng_ptr\fP\fB, png_alloc_size_t \fIsize\fP\fB);\fP +\fBpng_voidp png_malloc_default (png_structp \fP\fIpng_ptr\fP\fB, png_alloc_size_t \fIsize\fP\fB);\fP \fI\fB -\fBvoidp png_memcpy (png_voidp \fP\fIs1\fP\fB, png_voidp \fP\fIs2\fP\fB, png_size_t \fIsize\fP\fB);\fP +\fBpng_voidp png_malloc_warn (png_structp \fP\fIpng_ptr\fP\fB, png_alloc_size_t \fIsize\fP\fB);\fP \fI\fB -\fBvoidp png_memset (png_voidp \fP\fIs1\fP\fB, int \fP\fIvalue\fP\fB, png_size_t \fIsize\fP\fB);\fP +\fBpng_uint_32 png_permit_mng_features (png_structp \fP\fIpng_ptr\fP\fB, png_uint_32 \fImng_features_permitted\fP\fB);\fP \fI\fB @@ -354,6 +452,14 @@ libpng \- Portable Network Graphics (PNG) Reference Library 1.4.0 \fI\fB +\fBpng_size_t png_process_data_pause \fP\fI(png_structp\fP\fB, int \fIsave\fP\fB);\fP + +\fI\fB + +\fBpng_uint_32 png_process_data_skip \fI(png_structp\fP\fB);\fP + +\fI\fB + \fBvoid png_progressive_combine_row (png_structp \fP\fIpng_ptr\fP\fB, png_bytep \fP\fIold_row\fP\fB, png_bytep \fInew_row\fP\fB);\fP \fI\fB @@ -386,7 +492,11 @@ libpng \- Portable Network Graphics (PNG) Reference Library 1.4.0 \fI\fB -\fBpng_save_int_32 (png_bytep \fP\fIbuf\fP\fB, png_int_32 \fIi\fP\fB);\fP +\fBint png_reset_zstream (png_structp \fIpng_ptr\fP\fB);\fP + +\fI\fB + +\fBvoid png_save_int_32 (png_bytep \fP\fIbuf\fP\fB, png_int_32 \fIi\fP\fB);\fP \fI\fB @@ -402,10 +512,26 @@ libpng \- Portable Network Graphics (PNG) Reference Library 1.4.0 \fI\fB +\fBvoid png_set_alpha_mode (png_structp \fP\fIpng_ptr\fP\fB, int \fP\fImode\fP\fB, double \fIoutput_gamma\fP\fB);\fP + +\fI\fB + +\fBvoid png_set_alpha_mode_fixed (png_structp \fP\fIpng_ptr\fP\fB, int \fP\fImode\fP\fB, png_fixed_point \fIoutput_gamma\fP\fB);\fP + +\fI\fB + \fBvoid png_set_background (png_structp \fP\fIpng_ptr\fP\fB, png_color_16p \fP\fIbackground_color\fP\fB, int \fP\fIbackground_gamma_code\fP\fB, int \fP\fIneed_expand\fP\fB, double \fIbackground_gamma\fP\fB);\fP \fI\fB +\fBvoid png_set_background_fixed (png_structp \fP\fIpng_ptr\fP\fB, png_color_16p \fP\fIbackground_color\fP\fB, int \fP\fIbackground_gamma_code\fP\fB, int \fP\fIneed_expand\fP\fB, png_uint_32 \fIbackground_gamma\fP\fB);\fP + +\fI\fB + +\fBvoid png_set_benign_errors (png_structp \fP\fIpng_ptr\fP\fB, int \fIallowed\fP\fB);\fP + +\fI\fB + \fBvoid png_set_bgr (png_structp \fIpng_ptr\fP\fB);\fP \fI\fB @@ -450,19 +576,19 @@ libpng \- Portable Network Graphics (PNG) Reference Library 1.4.0 \fI\fB -\fBvoid png_set_dither (png_structp \fP\fIpng_ptr\fP\fB, png_colorp \fP\fIpalette\fP\fB, int \fP\fInum_palette\fP\fB, int \fP\fImaximum_colors\fP\fB, png_uint_16p \fP\fIhistogram\fP\fB, int \fIfull_dither\fP\fB);\fP +\fBvoid png_set_error_fn (png_structp \fP\fIpng_ptr\fP\fB, png_voidp \fP\fIerror_ptr\fP\fB, png_error_ptr \fP\fIerror_fn\fP\fB, png_error_ptr \fIwarning_fn\fP\fB);\fP \fI\fB -\fBvoid png_set_error_fn (png_structp \fP\fIpng_ptr\fP\fB, png_voidp \fP\fIerror_ptr\fP\fB, png_error_ptr \fP\fIerror_fn\fP\fB, png_error_ptr \fIwarning_fn\fP\fB);\fP +\fBvoid png_set_expand (png_structp \fIpng_ptr\fP\fB);\fP \fI\fB -\fBvoid png_set_expand (png_structp \fIpng_ptr\fP\fB);\fP +\fBvoid png_set_expand_16 (png_structp \fIpng_ptr\fP\fB);\fP \fI\fB -\fBvoid png_set_expand_gray_1_2_4_to_8(png_structp \fIpng_ptr\fP\fB);\fP +\fBvoid png_set_expand_gray_1_2_4_to_8 (png_structp \fIpng_ptr\fP\fB);\fP \fI\fB @@ -478,6 +604,10 @@ libpng \- Portable Network Graphics (PNG) Reference Library 1.4.0 \fI\fB +\fBvoid png_set_filter_heuristics_fixed (png_structp \fP\fIpng_ptr\fP\fB, int \fP\fIheuristic_method\fP\fB, int \fP\fInum_weights\fP\fB, png_fixed_point_p \fP\fIfilter_weights\fP\fB, png_fixed_point_p \fIfilter_costs\fP\fB);\fP + +\fI\fB + \fBvoid png_set_flush (png_structp \fP\fIpng_ptr\fP\fB, int \fInrows\fP\fB);\fP \fI\fB @@ -486,6 +616,10 @@ libpng \- Portable Network Graphics (PNG) Reference Library 1.4.0 \fI\fB +\fBvoid png_set_gamma_fixed (png_structp \fP\fIpng_ptr\fP\fB, png_uint_32 \fP\fIscreen_gamma\fP\fB, png_uint_32 \fIdefault_file_gamma\fP\fB);\fP + +\fI\fB + \fBvoid png_set_gAMA (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, double \fIfile_gamma\fP\fB);\fP \fI\fB @@ -494,7 +628,7 @@ libpng \- Portable Network Graphics (PNG) Reference Library 1.4.0 \fI\fB -\fBvoid png_set_gray_1_2_4_to_8(png_structp \fIpng_ptr\fP\fB);\fP +\fBvoid png_set_gray_1_2_4_to_8 (png_structp \fIpng_ptr\fP\fB);\fP \fI\fB @@ -506,7 +640,7 @@ libpng \- Portable Network Graphics (PNG) Reference Library 1.4.0 \fI\fB -\fBvoid png_set_iCCP (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_charp \fP\fIname\fP\fB, int \fP\fIcompression_type\fP\fB, png_charp \fP\fIprofile\fP\fB, png_uint_32 \fIproflen\fP\fB);\fP +\fBvoid png_set_iCCP (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_const_charp \fP\fIname\fP\fB, int \fP\fIcompression_type\fP\fB, png_const_bytep \fP\fIprofile\fP\fB, png_uint_32 \fIproflen\fP\fB);\fP \fI\fB @@ -538,7 +672,15 @@ libpng \- Portable Network Graphics (PNG) Reference Library 1.4.0 \fI\fB -\fBvoid png_set_mem_fn(png_structp \fP\fIpng_ptr\fP\fB, png_voidp \fP\fImem_ptr\fP\fB, png_malloc_ptr \fP\fImalloc_fn\fP\fB, png_free_ptr \fIfree_fn\fP\fB);\fP +\fBvoid png_set_chunk_malloc_max (png_structp \fP\fIpng_ptr\fP\fB, png_alloc_size_t \fIuser_chunk_cache_max\fP\fB);\fP + +\fI\fB + +\fBvoid png_set_compression_buffer_size (png_structp \fP\fIpng_ptr\fP\fB, png_uint_32 \fIsize\fP\fB);\fP + +\fI\fB + +\fBvoid png_set_mem_fn (png_structp \fP\fIpng_ptr\fP\fB, png_voidp \fP\fImem_ptr\fP\fB, png_malloc_ptr \fP\fImalloc_fn\fP\fB, png_free_ptr \fIfree_fn\fP\fB);\fP \fI\fB @@ -554,7 +696,7 @@ libpng \- Portable Network Graphics (PNG) Reference Library 1.4.0 \fI\fB -\fBvoid png_set_palette_to_rgb(png_structp \fIpng_ptr\fP\fB);\fP +\fBvoid png_set_palette_to_rgb (png_structp \fIpng_ptr\fP\fB);\fP \fI\fB @@ -574,6 +716,10 @@ libpng \- Portable Network Graphics (PNG) Reference Library 1.4.0 \fI\fB +\fBvoid png_set_quantize (png_structp \fP\fIpng_ptr\fP\fB, png_colorp \fP\fIpalette\fP\fB, int \fP\fInum_palette\fP\fB, int \fP\fImaximum_colors\fP\fB, png_uint_16p \fP\fIhistogram\fP\fB, int \fIfull_quantize\fP\fB);\fP + +\fI\fB + \fBvoid png_set_read_fn (png_structp \fP\fIpng_ptr\fP\fB, png_voidp \fP\fIio_ptr\fP\fB, png_rw_ptr \fIread_data_fn\fP\fB);\fP \fI\fB @@ -582,6 +728,10 @@ libpng \- Portable Network Graphics (PNG) Reference Library 1.4.0 \fI\fB +\fBvoid png_set_read_user_chunk_fn (png_structp \fP\fIpng_ptr\fP\fB, png_voidp \fP\fIuser_chunk_ptr\fP\fB, png_user_chunk_ptr \fIread_user_chunk_fn\fP\fB);\fP + +\fI\fB + \fBvoid png_set_read_user_transform_fn (png_structp \fP\fIpng_ptr\fP\fB, png_user_transform_ptr \fIread_user_transform_fn\fP\fB);\fP \fI\fB @@ -590,7 +740,7 @@ libpng \- Portable Network Graphics (PNG) Reference Library 1.4.0 \fI\fB -\fBvoid png_set_rgb_to_gray_fixed (png_structp \fP\fIpng_ptr\fP\fB, int error_action png_fixed_point \fP\fIred\fP\fB, png_fixed_point \fIgreen\fP\fB);\fP +\fBvoid png_set_rgb_to_gray_fixed (png_structp \fP\fIpng_ptr\fP\fB, int error_action png_uint_32 \fP\fIred\fP\fB, png_uint_32 \fIgreen\fP\fB);\fP \fI\fB @@ -602,7 +752,19 @@ libpng \- Portable Network Graphics (PNG) Reference Library 1.4.0 \fI\fB -\fBvoid png_set_sCAL (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_charp \fP\fIunit\fP\fB, double \fP\fIwidth\fP\fB, double \fIheight\fP\fB);\fP +\fBvoid png_set_sCAL (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, int \fP\fIunit\fP\fB, double \fP\fIwidth\fP\fB, double \fIheight\fP\fB);\fP + +\fI\fB + +\fBvoid png_set_sCAL_fixed (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, int \fP\fIunit\fP\fB, png_fixed_point \fP\fIwidth\fP\fB, png_fixed_point \fIheight\fP\fB);\fP + +\fI\fB + +\fBvoid png_set_sCAL_s (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, int \fP\fIunit\fP\fB, png_charp \fP\fIwidth\fP\fB, png_charp \fIheight\fP\fB);\fP + +\fI\fB + +\fBvoid png_set_scale_16 (png_structp \fIpng_ptr\fP\fB);\fP \fI\fB @@ -618,11 +780,11 @@ libpng \- Portable Network Graphics (PNG) Reference Library 1.4.0 \fI\fB -\fBvoid png_set_sRGB (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, int \fIintent\fP\fB);\fP +\fBvoid png_set_sRGB (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, int \fIsrgb_intent\fP\fB);\fP \fI\fB -\fBvoid png_set_sRGB_gAMA_and_cHRM (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, int \fIintent\fP\fB);\fP +\fBvoid png_set_sRGB_gAMA_and_cHRM (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, int \fIsrgb_intent\fP\fB);\fP \fI\fB @@ -634,6 +796,10 @@ libpng \- Portable Network Graphics (PNG) Reference Library 1.4.0 \fI\fB +\fBvoid png_set_strip_error_numbers (png_structp \fP\fIpng_ptr\fP\fB, png_uint_32 \fIstrip_mode\fP\fB);\fP + +\fI\fB + \fBvoid png_set_swap (png_structp \fIpng_ptr\fP\fB);\fP \fI\fB @@ -646,27 +812,43 @@ libpng \- Portable Network Graphics (PNG) Reference Library 1.4.0 \fI\fB -\fBvoid png_set_tIME (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_timep \fImod_time\fP\fB);\fP +\fBvoid png_set_text_compression_level (png_structp \fP\fIpng_ptr\fP\fB, int \fIlevel\fP\fB);\fP \fI\fB -\fBvoid png_set_tRNS (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_bytep \fP\fItrans\fP\fB, int \fP\fInum_trans\fP\fB, png_color_16p \fItrans_color\fP\fB);\fP +\fBvoid png_set_text_compression_mem_level (png_structp \fP\fIpng_ptr\fP\fB, int \fImem_level\fP\fB);\fP \fI\fB -\fBvoid png_set_tRNS_to_alpha(png_structp \fIpng_ptr\fP\fB);\fP +\fBvoid png_set_text_compression_strategy (png_structp \fP\fIpng_ptr\fP\fB, int \fIstrategy\fP\fB);\fP \fI\fB -\fBpng_uint_32 png_set_unknown_chunks (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_unknown_chunkp \fP\fIunknowns\fP\fB, int \fP\fInum\fP\fB, int \fIlocation\fP\fB);\fP +\fBvoid png_set_text_compression_window_bits (png_structp \fP\fIpng_ptr\fP\fB, int \fIwindow_bits\fP\fB);\fP \fI\fB -\fBvoid png_set_unknown_chunk_location(png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, int \fP\fIchunk\fP\fB, int \fIlocation\fP\fB);\fP +\fBvoid \fP\fIpng_set_text_compression_method\fP\fB, (png_structp \fP\fIpng_ptr\fP\fB, int \fImethod)\fP\fB);\fP \fI\fB -\fBvoid png_set_read_user_chunk_fn (png_structp \fP\fIpng_ptr\fP\fB, png_voidp \fP\fIuser_chunk_ptr\fP\fB, png_user_chunk_ptr \fIread_user_chunk_fn\fP\fB);\fP +\fBvoid png_set_tIME (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_timep \fImod_time\fP\fB);\fP + +\fI\fB + +\fBvoid png_set_tRNS (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_bytep \fP\fItrans_alpha\fP\fB, int \fP\fInum_trans\fP\fB, png_color_16p \fItrans_color\fP\fB);\fP + +\fI\fB + +\fBvoid png_set_tRNS_to_alpha (png_structp \fIpng_ptr\fP\fB);\fP + +\fI\fB + +\fBpng_uint_32 png_set_unknown_chunks (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, png_unknown_chunkp \fP\fIunknowns\fP\fB, int \fP\fInum\fP\fB, int \fIlocation\fP\fB);\fP + +\fI\fB + +\fBvoid png_set_unknown_chunk_location (png_structp \fP\fIpng_ptr\fP\fB, png_infop \fP\fIinfo_ptr\fP\fB, int \fP\fIchunk\fP\fB, int \fIlocation\fP\fB);\fP \fI\fB @@ -690,10 +872,6 @@ libpng \- Portable Network Graphics (PNG) Reference Library 1.4.0 \fI\fB -\fBvoid png_set_compression_buffer_size(png_structp \fP\fIpng_ptr\fP\fB, png_uint_32 \fIsize\fP\fB);\fP - -\fI\fB - \fBint png_sig_cmp (png_bytep \fP\fIsig\fP\fB, png_size_t \fP\fIstart\fP\fB, png_size_t \fInum_to_check\fP\fB);\fP \fI\fB @@ -773,14 +951,14 @@ library supports encoding, decoding, and various manipulations of the Portable Network Graphics (PNG) format image files. It uses the .IR zlib(3) compression library. -Following is a copy of the libpng.txt file that accompanies libpng. +Following is a copy of the libpng-manual.txt file that accompanies libpng. .SH LIBPNG.TXT -libpng.txt - A description on how to use and modify libpng +libpng-manual.txt - A description on how to use and modify libpng - libpng version 1.4.0 - January 3, 2010 + libpng version 1.5.4 - July 7, 2011 Updated and distributed by Glenn Randers-Pehrson <glennrp at users.sourceforge.net> - Copyright (c) 1998-2009 Glenn Randers-Pehrson + Copyright (c) 1998-2011 Glenn Randers-Pehrson This document is released under the libpng license. For conditions of distribution and use, see the disclaimer @@ -788,9 +966,9 @@ libpng.txt - A description on how to use and modify libpng Based on: - libpng versions 0.97, January 1998, through 1.4.0 - January 3, 2010 + libpng versions 0.97, January 1998, through 1.5.4 - July 7, 2011 Updated and distributed by Glenn Randers-Pehrson - Copyright (c) 1998-2009 Glenn Randers-Pehrson + Copyright (c) 1998-2011 Glenn Randers-Pehrson libpng 1.0 beta 6 version 0.96 May 28, 1997 Updated and distributed by Andreas Dilger @@ -876,34 +1054,181 @@ same instance of a structure. .SH II. Structures There are two main structures that are important to libpng, png_struct -and png_info. The first, png_struct, is an internal structure that -will not, for the most part, be used by a user except as the first -variable passed to every libpng function call. +and png_info. Both are internal structures that are no longer exposed +in the libpng interface (as of libpng 1.5.0). The png_info structure is designed to provide information about the PNG file. At one time, the fields of png_info were intended to be directly accessible to the user. However, this tended to cause problems with applications using dynamically loaded libraries, and as a result a set of interface functions for png_info (the png_get_*() and png_set_*() -functions) was developed. The fields of png_info are still available for -older applications, but it is suggested that applications use the new -interfaces if at all possible. - -Applications that do make direct access to the members of png_struct (except -for png_ptr->jmpbuf) must be recompiled whenever the library is updated, -and applications that make direct access to the members of png_info must -be recompiled if they were compiled or loaded with libpng version 1.0.6, -in which the members were in a different order. In version 1.0.7, the -members of the png_info structure reverted to the old order, as they were -in versions 0.97c through 1.0.5. Starting with version 2.0.0, both -structures are going to be hidden, and the contents of the structures will -only be accessible through the png_get/png_set functions. +functions) was developed. + +The png_struct structure is the object used by the library to decode a +single image. As of 1.5.0 this structure is also not exposed. + +Almost all libpng APIs require a pointer to a png_struct as the first argument. +Many (in particular the png_set and png_get APIs) also require a pointer +to png_info as the second argument. Some application visible macros +defined in png.h designed for basic data access (reading and writing +integers in the PNG format) break this rule, but it's almost always safe +to assume that a (png_struct*) has to be passed to call an API function. The png.h header file is an invaluable reference for programming with libpng. And while I'm on the topic, make sure you include the libpng header file: #include <png.h> +.SS Types + +The png.h header file defines a number of integral types used by the +APIs. Most of these are fairly obvious; for example types corresponding +to integers of particular sizes and types for passing color values. + +One exception is how non-integral numbers are handled. For application +convenience most APIs that take such numbers have C (double) arguments, +however internally PNG, and libpng, use 32 bit signed integers and encode +the value by multiplying by 100,000. As of libpng 1.5.0 a convenience +macro PNG_FP_1 is defined in png.h along with a type (png_fixed_point) +which is simply (png_int_32). + +All APIs that take (double) arguments also have an matching API that +takes the corresponding fixed point integer arguments. The fixed point +API has the same name as the floating point one with _fixed appended. +The actual range of values permitted in the APIs is frequently less than +the full range of (png_fixed_point) (-21474 to +21474). When APIs require +a non-negative argument the type is recorded as png_uint_32 above. Consult +the header file and the text below for more information. + +Special care must be take with sCAL chunk handling because the chunk itself +uses non-integral values encoded as strings containing decimal floating point +numbers. See the comments in the header file. + +.SS Configuration + +The main header file function declarations are frequently protected by C +preprocessing directives of the form: + + #ifdef PNG_feature_SUPPORTED + declare-function + #endif + +The library can be built without support for these APIs, although a +standard build will have all implemented APIs. Application programs +should check the feature macros before using an API for maximum +portability. From libpng 1.5.0 the feature macros set during the build +of libpng are recorded in the header file "pnglibconf.h" and this file +is always included by png.h. + +If you don't need to change the library configuration from the default skip to +the next section ("Reading"). + +Notice that some of the makefiles in the 'scripts' directory and (in 1.5.0) all +of the build project files in the 'projects' directory simply copy +scripts/pnglibconf.h.prebuilt to pnglibconf.h. This means that these build +systems do not permit easy auto-configuration of the library - they only +support the default configuration. + +The easiest way to make minor changes to the libpng configuration when +auto-configuration is supported is to add definitions to the command line +using (typically) CPPFLAGS. For example: + +CPPFLAGS=-DPNG_NO_FLOATING_ARITHMETIC + +will change the internal libpng math implementation for gamma correction and +other arithmetic calculations to fixed point, avoiding the need for fast +floating point support. The result can be seen in the generated pnglibconf.h - +make sure it contains the changed feature macro setting. + +If you need to make more extensive configuration changes - more than one or two +feature macro settings - you can either add -DPNG_USER_CONFIG to the build +command line and put a list of feature macro settings in pngusr.h or you can set +DFA_XTRA (a makefile variable) to a file containing the same information in the +form of 'option' settings. + +A. Changing pnglibconf.h + +A variety of methods exist to build libpng. Not all of these support +reconfiguration of pnglibconf.h. To reconfigure pnglibconf.h it must either be +rebuilt from scripts/pnglibconf.dfa using awk or it must be edited by hand. + +Hand editing is achieved by copying scripts/pnglibconf.h.prebuilt and changing +the lines defining the supported features, paying very close attention to +the 'option' information in scripts/pnglibconf.dfa that describes those +features and their requirements. This is easy to get wrong. + +B. Configuration using DFA_XTRA + +Rebuilding from pnglibconf.dfa is easy if a functioning 'awk', or a later +variant such as 'nawk' or 'gawk', is available. The configure build will +automatically find an appropriate awk and build pnglibconf.h. +scripts/pnglibconf.mak contains a set of make rules for doing the same thing if +configure is not used, and many of the makefiles in the scripts directory use +this approach. + +When rebuilding simply write new file containing changed options and set +DFA_XTRA to the name of this file. This causes the build to append the new file +to the end of scripts/pnglibconf.dfa. pngusr.dfa should contain lines of the +following forms: + +everything = off + +This turns all optional features off. Include it at the start of pngusr.dfa to +make it easier to build a minimal configuration. You will need to turn at least +some features on afterward to enable either reading or writing code, or both. + +option feature on +option feature off + +Enable or disable a single feature. This will automatically enable other +features required by a feature that is turned on or disable other features that +require a feature which is turned off. Conflicting settings will cause an error +message to be emitted by awk. + +setting feature default value + +Changes the default value of setting 'feature' to 'value'. There are a small +number of settings listed at the top of pnglibconf.h, they are documented in the +source code. Most of these values have performance implications for the library +but most of them have no visible effect on the API. Some can also be overridden +from the API. + +C. Configuration using PNG_USR_CONFIG + +If -DPNG_USR_CONFIG is added to the CFLAGS when pnglibconf.h is built the file +pngusr.h will automatically be included before the options in +scripts/pnglibconf.dfa are processed. pngusr.h should contain only macro +definitions turning features on or off or setting settings. + +Apart from the global setting "everything = off" all the options listed above +can be set using macros in pngusr.h: + +#define PNG_feature_SUPPORTED + +is equivalent to: + +option feature on + +#define PNG_NO_feature + +is equivalent to: + +option feature off + +#define PNG_feature value + +is equivalent to: + +setting feature default value + +Notice that in both cases, pngusr.dfa and pngusr.h, the contents of the +pngusr file you supply override the contents of scripts/pnglibconf.dfa + +If confusing or incomprehensible behavior results it is possible to +examine the intermediate file pnglibconf.dfn to find the full set of +dependency information for each setting and option. Simply locate the +feature in the file and read the C comments that precede it. + .SH III. Reading We'll now walk you through the possible functions to call when reading @@ -939,13 +1264,15 @@ Customizing libpng. FILE *fp = fopen(file_name, "rb"); if (!fp) { - return (ERROR); + return (ERROR); } + fread(header, 1, number, fp); is_png = !png_sig_cmp(header, 0, number); + if (!is_png) { - return (NOT_PNG); + return (NOT_PNG); } @@ -961,33 +1288,27 @@ The structure allocation functions quietly return NULL if they fail to create the structure, so your application should check for that. png_structp png_ptr = png_create_read_struct - (PNG_LIBPNG_VER_STRING, (png_voidp)user_error_ptr, + (PNG_LIBPNG_VER_STRING, (png_voidp)user_error_ptr, user_error_fn, user_warning_fn); + if (!png_ptr) - return (ERROR); + return (ERROR); png_infop info_ptr = png_create_info_struct(png_ptr); + if (!info_ptr) { - png_destroy_read_struct(&png_ptr, + png_destroy_read_struct(&png_ptr, (png_infopp)NULL, (png_infopp)NULL); - return (ERROR); - } - - png_infop end_info = png_create_info_struct(png_ptr); - if (!end_info) - { - png_destroy_read_struct(&png_ptr, &info_ptr, - (png_infopp)NULL); - return (ERROR); + return (ERROR); } If you want to use your own memory allocation routines, -define PNG_USER_MEM_SUPPORTED and use +use a libpng that was built with PNG_USER_MEM_SUPPORTED defined, and use png_create_read_struct_2() instead of png_create_read_struct(): png_structp png_ptr = png_create_read_struct_2 - (PNG_LIBPNG_VER_STRING, (png_voidp)user_error_ptr, + (PNG_LIBPNG_VER_STRING, (png_voidp)user_error_ptr, user_error_fn, user_warning_fn, (png_voidp) user_mem_ptr, user_malloc_fn, user_free_fn); @@ -999,7 +1320,7 @@ handling and memory alloc/free functions. When libpng encounters an error, it expects to longjmp back to your routine. Therefore, you will need to call setjmp and pass your png_jmpbuf(png_ptr). If you read the file from different -routines, you will need to update the jmpbuf field every time you enter +routines, you will need to update the longjmp buffer every time you enter a new routine that will call a png_*() function. See your documentation of setjmp/longjmp for your compiler for more @@ -1011,16 +1332,23 @@ free any memory. if (setjmp(png_jmpbuf(png_ptr))) { - png_destroy_read_struct(&png_ptr, &info_ptr, + png_destroy_read_struct(&png_ptr, &info_ptr, &end_info); - fclose(fp); - return (ERROR); + fclose(fp); + return (ERROR); } +Pass (png_infopp)NULL instead of &end_info if you didn't create +an end_info structure. + If you would rather avoid the complexity of setjmp/longjmp issues, -you can compile libpng with PNG_SETJMP_NOT_SUPPORTED, in which case +you can compile libpng with PNG_NO_SETJMP, in which case errors will result in a call to PNG_ABORT() which defaults to abort(). +You can #define PNG_ABORT() to a function that does something +more useful than abort(), as long as your function does not +return. + Now you need to set up the input code. The default for libpng is to use the C function fread(). If you use this, you will need to pass a valid FILE * in the function png_init_io(). Be sure that the file is @@ -1037,12 +1365,46 @@ libpng know that there are some bytes missing from the start of the file. png_set_sig_bytes(png_ptr, number); +You can change the zlib compression buffer size to be used while +reading compressed data with + + png_set_compression_buffer_size(png_ptr, buffer_size); + +where the default size is 8192 bytes. Note that the buffer size +is changed immediately and the buffer is reallocated immediately, +instead of setting a flag to be acted upon later. + +If you want CRC errors to be handled in a different manner than +the default, use + + png_set_crc_action(png_ptr, crit_action, ancil_action); + +The values for png_set_crc_action() say how libpng is to handle CRC errors in +ancillary and critical chunks, and whether to use the data contained +therein. Note that it is impossible to "discard" data in a critical +chunk. + +Choices for (int) crit_action are + PNG_CRC_DEFAULT 0 error/quit + PNG_CRC_ERROR_QUIT 1 error/quit + PNG_CRC_WARN_USE 3 warn/use data + PNG_CRC_QUIET_USE 4 quiet/use data + PNG_CRC_NO_CHANGE 5 use the current value + +Choices for (int) ancil_action are + PNG_CRC_DEFAULT 0 error/quit + PNG_CRC_ERROR_QUIT 1 error/quit + PNG_CRC_WARN_DISCARD 2 warn/discard data + PNG_CRC_WARN_USE 3 warn/use data + PNG_CRC_QUIET_USE 4 quiet/use data + PNG_CRC_NO_CHANGE 5 use the current value + .SS Setting up callback code You can set up a callback function to handle any unknown chunks in the input stream. You must supply the function - read_chunk_callback(png_ptr ptr, + read_chunk_callback(png_structp png_ptr, png_unknown_chunkp chunk); { /* The unknown chunk structure contains your @@ -1088,8 +1450,8 @@ called after each row has been read, which you can use to control a progress meter or the like. It's demonstrated in pngtest.c. You must supply a function - void read_row_callback(png_ptr ptr, png_uint_32 row, - int pass); + void read_row_callback(png_structp png_ptr, + png_uint_32 row, int pass); { /* put your code here */ } @@ -1100,6 +1462,19 @@ To inform libpng about your function, use png_set_read_status_fn(png_ptr, read_row_callback); +When this function is called the row has already been completely processed and +the 'row' and 'pass' refer to the next row to be handled. For the +non-interlaced case the row that was just handled is simply one less than the +passed in row number, and pass will always be 0. For the interlaced case the +same applies unless the row value is 0, in which case the row just handled was +the last one from one of the preceding passes. Because interlacing may skip a +pass you cannot be sure that the preceding pass is just 'pass-1', if you really +need to know what the last pass is record (row,pass) from the callback and use +the last recorded value each time. + +As with the user transform you can find the output row using the +PNG_ROW_FROM_PASS_ROW macro. + .SS Unknown-chunk handling Now you get to set the way the library processes unknown chunks in the @@ -1115,14 +1490,17 @@ chunk types. To change this, you can call: 1: ignore; do not keep 2: keep only if safe-to-copy 3: keep even if unsafe-to-copy + You can use these definitions: PNG_HANDLE_CHUNK_AS_DEFAULT 0 PNG_HANDLE_CHUNK_NEVER 1 PNG_HANDLE_CHUNK_IF_SAFE 2 PNG_HANDLE_CHUNK_ALWAYS 3 + chunk_list - list of chunks affected (a byte string, five bytes per chunk, NULL or '\0' if num_chunks is 0) + num_chunks - number of chunks affected; if 0, all unknown chunks are affected. If nonzero, only the chunks in the list are affected @@ -1158,8 +1536,10 @@ callback function: #if defined(PNG_UNKNOWN_CHUNKS_SUPPORTED) /* ignore all unknown chunks: */ png_set_keep_unknown_chunks(read_ptr, 1, NULL, 0); + /* except for vpAg: */ png_set_keep_unknown_chunks(read_ptr, 2, vpAg, 1); + /* also ignore unused known chunks: */ png_set_keep_unknown_chunks(read_ptr, 1, unused_chunks, (int)sizeof(unused_chunks)/5); @@ -1172,7 +1552,7 @@ large as 2^31-1 (0x7fffffff), or about 2.147 billion rows and columns. Since very few applications really need to process such large images, we have imposed an arbitrary 1-million limit on rows and columns. Larger images will be rejected immediately with a png_error() call. If -you wish to override this limit, you can use +you wish to change this limit, you can use png_set_user_limits(png_ptr, width_max, height_max); @@ -1182,6 +1562,10 @@ anyway because of potential buffer overflow conditions). You should put this statement after you create the PNG structure and before calling png_read_info(), png_read_png(), or png_process_data(). + +When writing a PNG datastream, put this statement before calling +png_write_info() or png_write_png(). + If you need to retrieve the limits that are being applied, use width_max = png_get_user_width_max(png_ptr); @@ -1200,6 +1584,246 @@ where 0x7fffffffL means unlimited. You can retrieve this limit with This limit also applies to the number of buffers that can be allocated by png_decompress_chunk() while decompressing iTXt, zTXt, and iCCP chunks. +You can also set a limit on the amount of memory that a compressed chunk +other than IDAT can occupy, with + + png_set_chunk_malloc_max(png_ptr, user_chunk_malloc_max); + +and you can retrieve the limit with + + chunk_malloc_max = png_get_chunk_malloc_max(png_ptr); + +Any chunks that would cause either of these limits to be exceeded will +be ignored. + +.SS Information about your system + +If you intend to display the PNG or to incorporate it in other image data you +need to tell libpng information about your display or drawing surface so that +libpng can convert the values in the image to match the display. + +From libpng-1.5.4 this information can be set before reading the PNG file +header. In earlier versions png_set_gamma() existed but behaved incorrectly if +called before the PNG file header had been read and png_set_alpha_mode() did not +exist. + +If you need to support versions prior to libpng-1.5.4 test the version number +and follow the procedures described in the appropriate manual page. + +You give libpng the encoding expected by your system expressed as a 'gamma' +value. You can also specify a default encoding for the PNG file in +case the required information is missing from the file. By default libpng +assumes that the PNG data matches your system, to keep this default call: + + png_set_gamma(png_ptr, screen_gamma, 1/screen_gamma/*file gamma*/); + +or you can use the fixed point equivalent: + + png_set_gamma_fixed(png_ptr, PNG_FP_1*screen_gamma, PNG_FP_1/screen_gamma); + +If you don't know the gamma for you system it is probably 2.2 - a good +approximation to the IEC standard for display systems (sRGB). If images are +too contrasty or washed out you got the value wrong - check your system +documentation! + +Many systems permit the system gamma to be changed via a lookup table in the +display driver, a few systems, including older Macs, change the response by +default. As of 1.5.4 three special values are available to handle common +situations: + + PNG_DEFAULT_sRGB: Indicates that the system conforms to the IEC 61966-2-1 + standard. This matches almost all systems. + PNG_GAMMA_MAC_18: Indicates that the system is an older (pre Mac OS 10.6) + Apple Macintosh system with the default settings. + PNG_GAMMA_LINEAR: Just the fixed point value for 1.0 - indicates that the + system expects data with no gamma encoding. + +You would use the linear (unencoded) value if you need to process the pixel +values further because this avoids the need to decode and reencode each +component value whenever arithmetic is performed. A lot of graphics software +uses linear values for this reason, often with higher precision component values +to preserve overall accuracy. + +The second thing you may need to tell libpng about is how your system handles +alpha channel information. Some, but not all, PNG files contain an alpha +channel. To display these files correctly you need to compose the data onto a +suitable background, as described in the PNG specification. + +Libpng only supports composing onto a single color (using png_set_background; +see below.) Otherwise you must do the composition yourself and, in this case, +you may need to call png_set_alpha_mode: + + png_set_alpha_mode(png_ptr, mode, screen_gamma); + +The screen_gamma value is the same as the argument to png_set_gamma, however how +it affects the output depends on the mode. png_set_alpha_mode() sets the file +gamma default to 1/screen_gamma, so normally you don't need to call +png_set_gamma. If you need different defaults call png_set_gamma() before +png_set_alpha_mode() - if you call it after it will override the settings made +by png_set_alpha_mode(). + +The mode is as follows: + + PNG_ALPHA_PNG: The data is encoded according to the PNG specification. Red, +green and blue, or gray, components are gamma encoded color +values and are not premultiplied by the alpha value. The +alpha value is a linear measure of the contribution of the +pixel to the corresponding final output pixel. + +You should normally use this format if you intend to perform +color correction on the color values; most, maybe all, color +correction software has no handling for the alpha channel and, +anyway, the math to handle pre-multiplied component values is +unnecessarily complex. + +Before you do any arithmetic on the component values you need +to remove the gamma encoding and multiply out the alpha +channel. See the PNG specification for more detail. It is +important to note that when an image with an alpha channel is +scaled, linear encoded, pre-multiplied component values must +be used! + +The remaining modes assume you don't need to do any further color correction or +that if you do your color correction software knows all about alpha (it +probably doesn't!) + + PNG_ALPHA_STANDARD: The data libpng produces is encoded in the standard way +assumed by most correctly written graphics software. +The gamma encoding will be removed by libpng and the +linear component values will be pre-multiplied by the +alpha channel. + +With this format the final image must be re-encoded to +match the display gamma before the image is displayed. +If your system doesn't do that, yet still seems to +perform arithmetic on the pixels without decoding them, +it is broken - check out the modes below. + +With PNG_ALPHA_STANDARD libpng always produces linear +component values, whatever screen_gamma you supply. The +screen_gamma value is, however, used as a default for +the file gamma if the PNG file has no gamma information. + +If you call png_set_gamma() after png_set_alpha_mode() you +will override the linear encoding. Instead the +pre-multiplied pixel values will be gamma encoded but +the alpha channel will still be linear. This may +actually match the requirements of some broken software, +but it is unlikely. + +While linear 8-bit data is often used it has +insufficient precision for any image with a reasonable +dynamic range. To avoid problems, and if your software +supports it, use png_set_expand_16() to force all +components to 16 bits. + + PNG_ALPHA_OPTIMIZED: This mode is the same as PNG_ALPHA_STANDARD except that +completely opaque pixels are gamma encoded according to +the screen_gamma value. Pixels with alpha less than 1.0 +will still have linear components. + +Use this format if you have control over your +compositing software and do don't do other arithmetic +(such as scaling) on the data you get from libpng. Your +compositing software can simply copy opaque pixels to +the output but still has linear values for the +non-opaque pixels. + +In normal compositing, where the alpha channel encodes +partial pixel coverage (as opposed to broad area +translucency), the inaccuracies of the 8-bit +representation of non-opaque pixels are irrelevant. + +You can also try this format if your software is broken; +it might look better. + + PNG_ALPHA_BROKEN: This is PNG_ALPHA_STANDARD however all component values, +including the alpha channel are gamma encoded. This is +an appropriate format to try if your software, or more +likely hardware, is totally broken: if it performs +linear arithmetic directly on gamma encoded values. + +In most cases of broken software or hardware the bug in the final display +manifests as a subtle halo around composited parts of the image. You may not +even perceive this as a halo; the composited part of the image may simply appear +separate from the background, as though it had been cut out of paper and pasted +on afterward. + +If you don't have to deal with bugs in software or hardware, or if you can fix +them, there are three recommended ways of using png_set_alpha_mode(): + + png_set_alpha_mode(png_ptr, PNG_ALPHA_PNG, + screen_gamma); + +You can do color correction on the result (libpng does not currently +support color correction internally.) When you handle the alpha channel +you need to undo the gamma encoding and multiply out the alpha. + + png_set_alpha_mode(png_ptr, PNG_ALPHA_STANDARD, + screen_gamma); + png_set_expand_16(png_ptr); + +If you are using the high level interface don't call png_set_expand_16(); +instead pass PNG_TRANSFORM_EXPAND_16 to the interface. + +With this mode you can't do color correction, but you can do arithmetic, +including composition and scaling, on the data without further processing. + + png_set_alpha_mode(png_ptr, PNG_ALPHA_OPTIMIZED, + screen_gamma); + +You can avoid the expansion to 16-bit components with this mode, but you +lose the ability to scale the image or perform other linear arithmetic. +All you can do is compose the result onto a matching output. Since this +mode is libpng specific you also need to write your own composition +software. + +If you don't need, or can't handle, the alpha channel you can call +png_set_background() to remove it by compositing against a fixed color. Don't +call png_set_strip_alpha() to do this - it will leave spurious pixel values in +transparent parts of this image. + + png_set_background(png_ptr, &background_color, + PNG_BACKGROUND_GAMMA_SCREEN, 0, 1); + +The background_color is an RGB or grayscale value according to the data format +libpng will produce for you. Because you don't yet know the format of the PNG +file if you call png_set_background at this point you must arrange for the +format produced by libpng to always have 8-bit or 16-bit components and then +store the color as an 8-bit or 16-bit color as appropriate. The color contains +separate gray and RGB component values, so you can let libpng produce gray or +RGB output according to the input format, but low bit depth grayscale images +must always be converted to at least 8-bit format. (Even low low bit depth +grayscale images can't have an alpha channel they can have a transparent +color!) + +You set the transforms you need later, either as flags to the high level +interface or libpng API calls for the low level interface. For reference the +settings and API calls required are: + +8-bit values: + PNG_TRANSFORM_SCALE_16 | PNG_EXPAND + png_set_expand(png_ptr); png_set_scale_16(png_ptr); + + If you must get exactly the same inaccurate results + produced by default in versions prior to libpng-1.5.4, + use PNG_TRANSFORM_STRIP_16 and png_set_strip_16(png_ptr) + instead. + +16-bit values: + PNG_TRANSFORM_EXPAND_16 + png_set_expand_16(png_ptr); + +In either case palette image data will be expanded to RGB. If you just want +color data you can add PNG_TRANSFORM_GRAY_TO_RGB or png_set_gray_to_rgb(png_ptr) +to the list. + +Calling png_set_background before the PNG file header is read will not work +prior to libpng-1.5.4. Because the failure may result in unexpected warnings or +errors it is therefore much safer to call png_set_background after the head has +been read. Unfortunately this means that prior to libpng-1.5.4 it cannot be +used with the high level interface. + .SS The high-level read interface At this point there are two ways to proceed; through the high-level @@ -1209,8 +1833,10 @@ the entire image into memory, and (b) the input transformations you want to do are limited to the following set: PNG_TRANSFORM_IDENTITY No transformation - PNG_TRANSFORM_STRIP_16 Strip 16-bit samples to - 8 bits + PNG_TRANSFORM_SCALE_16 Strip 16-bit samples to + 8-bit accurately + PNG_TRANSFORM_STRIP_16 Chop 16-bit samples to + 8-bit less accurately PNG_TRANSFORM_STRIP_ALPHA Discard the alpha channel PNG_TRANSFORM_PACKING Expand 1, 2 and 4-bit samples to bytes @@ -1229,9 +1855,10 @@ you want to do are limited to the following set: PNG_TRANSFORM_SWAP_ENDIAN Byte-swap 16-bit samples PNG_TRANSFORM_GRAY_TO_RGB Expand grayscale samples to RGB (or GA to RGBA) + PNG_TRANSFORM_EXPAND_16 Expand samples to 16 bits (This excludes setting a background color, doing gamma transformation, -dithering, and setting filler.) If this is the case, simply do this: +quantizing, and setting filler.) If this is the case, simply do this: png_read_png(png_ptr, info_ptr, png_transforms, NULL) @@ -1260,17 +1887,22 @@ row_pointers prior to calling png_read_png() with if (height > PNG_UINT_32_MAX/png_sizeof(png_byte)) png_error (png_ptr, - "Image is too tall to process in memory"); + "Image is too tall to process in memory"); + if (width > PNG_UINT_32_MAX/pixel_size) png_error (png_ptr, - "Image is too wide to process in memory"); + "Image is too wide to process in memory"); + row_pointers = png_malloc(png_ptr, - height*png_sizeof(png_bytep)); + height*png_sizeof(png_bytep)); + for (int i=0; i<height, i++) row_pointers[i]=NULL; /* security precaution */ + for (int i=0; i<height, i++) row_pointers[i]=png_malloc(png_ptr, - width*pixel_size); + width*pixel_size); + png_set_rows(png_ptr, info_ptr, &row_pointers); Alternatively you could allocate your image in one big block and define @@ -1280,7 +1912,7 @@ If you use png_set_rows(), the application is responsible for freeing row_pointers (and row_pointers[i], if they were separately allocated). If you don't allocate row_pointers ahead of time, png_read_png() will -do it, and it'll be free'ed when you call png_destroy_*(). +do it, and it'll be free'ed by libpng when you call png_destroy_*(). .SS The low-level read interface @@ -1292,6 +1924,22 @@ call to png_read_info(). This will process all chunks up to but not including the image data. +This also copies some of the data from the PNG file into the decode structure +for use in later transformations. Important information copied in is: + +1) The PNG file gamma from the gAMA chunk. This overwrites the default value +provided by an earlier call to png_set_gamma or png_set_alpha_mode. + +2) Prior to libpng-1.5.4 the background color from a bKGd chunk. This +damages the information provided by an earlier call to png_set_background +resulting in expected behavior. Libpng-1.5.4 no longer does this. + +3) The number of significant bits in each component value. Libpng uses this to +optimize gamma handling by reducing the internal lookup table sizes. + +4) The transparent color information from a tRNS chunk. This can be modified by +a later call to png_set_tRNS. + .SS Querying the info structure Functions are used to get the information from the info_ptr once it @@ -1304,13 +1952,16 @@ in until png_read_end() has read the chunk data following the image. width - holds the width of the image in pixels (up to 2^31). + height - holds the height of the image in pixels (up to 2^31). + bit_depth - holds the bit depth of one of the image channels. (valid values are 1, 2, 4, 8, 16 and depend also on the color_type. See also significant bits (sBIT) below). + color_type - describes which color/alpha channels are present. PNG_COLOR_TYPE_GRAY @@ -1328,15 +1979,17 @@ in until png_read_end() has read the chunk data following the image. PNG_COLOR_MASK_COLOR PNG_COLOR_MASK_ALPHA + interlace_type - (PNG_INTERLACE_NONE or + PNG_INTERLACE_ADAM7) + + compression_type - (must be PNG_COMPRESSION_TYPE_BASE + for PNG 1.0) + filter_method - (must be PNG_FILTER_TYPE_BASE for PNG 1.0, and can also be PNG_INTRAPIXEL_DIFFERENCING if the PNG datastream is embedded in a MNG-1.0 datastream) - compression_type - (must be PNG_COMPRESSION_TYPE_BASE - for PNG 1.0) - interlace_type - (PNG_INTERLACE_NONE or - PNG_INTERLACE_ADAM7) Any or all of interlace_type, compression_type, or filter_method can be NULL if you are @@ -1351,28 +2004,38 @@ in until png_read_end() has read the chunk data following the image. width = png_get_image_width(png_ptr, info_ptr); + height = png_get_image_height(png_ptr, info_ptr); + bit_depth = png_get_bit_depth(png_ptr, info_ptr); + color_type = png_get_color_type(png_ptr, info_ptr); - filter_method = png_get_filter_type(png_ptr, + + interlace_type = png_get_interlace_type(png_ptr, info_ptr); + compression_type = png_get_compression_type(png_ptr, info_ptr); - interlace_type = png_get_interlace_type(png_ptr, + + filter_method = png_get_filter_type(png_ptr, info_ptr); channels = png_get_channels(png_ptr, info_ptr); + channels - number of channels of info for the color type (valid values are 1 (GRAY, PALETTE), 2 (GRAY_ALPHA), 3 (RGB), 4 (RGB_ALPHA or RGB + filler byte)) + rowbytes = png_get_rowbytes(png_ptr, info_ptr); + rowbytes - number of bytes needed to hold a row signature = png_get_signature(png_ptr, info_ptr); + signature - holds the signature read from the file (if any). The data is kept in the same offset it would be if the @@ -1392,16 +2055,24 @@ pointer into the info_ptr is returned for any complex types. png_get_PLTE(png_ptr, info_ptr, &palette, &num_palette); + palette - the palette for the file (array of png_color) + num_palette - number of entries in the palette - png_get_gAMA(png_ptr, info_ptr, &gamma); - gamma - the gamma the file is written - at (PNG_INFO_gAMA) + png_get_gAMA(png_ptr, info_ptr, &file_gamma); + png_get_gAMA_fixed(png_ptr, info_ptr, &int_file_gamma); + + file_gamma - the gamma at which the file is + written (PNG_INFO_gAMA) + + int_file_gamma - 100,000 times the gamma at which the + file is written png_get_sRGB(png_ptr, info_ptr, &srgb_intent); - srgb_intent - the rendering intent (PNG_INFO_sRGB) + + file_srgb_intent - the rendering intent (PNG_INFO_sRGB) The presence of the sRGB chunk means that the pixel data is in the sRGB color space. This chunk also @@ -1410,16 +2081,21 @@ pointer into the info_ptr is returned for any complex types. png_get_iCCP(png_ptr, info_ptr, &name, &compression_type, &profile, &proflen); - name - The profile name. - compression - The compression type; always - PNG_COMPRESSION_TYPE_BASE for PNG 1.0. - You may give NULL to this argument to - ignore it. - profile - International Color Consortium color - profile data. May contain NULs. - proflen - length of profile data in bytes. + + name - The profile name. + + compression_type - The compression type; always + PNG_COMPRESSION_TYPE_BASE for PNG 1.0. + You may give NULL to this argument to + ignore it. + + profile - International Color Consortium color + profile data. May contain NULs. + + proflen - length of profile data in bytes. png_get_sBIT(png_ptr, info_ptr, &sig_bit); + sig_bit - the number of significant bits for (PNG_INFO_sBIT) each of the gray, red, green, and blue channels, @@ -1428,50 +2104,66 @@ pointer into the info_ptr is returned for any complex types. png_get_tRNS(png_ptr, info_ptr, &trans_alpha, &num_trans, &trans_color); + trans_alpha - array of alpha (transparency) entries for palette (PNG_INFO_tRNS) + + num_trans - number of transparent entries + (PNG_INFO_tRNS) + trans_color - graylevel or color sample values of the single transparent color for non-paletted images (PNG_INFO_tRNS) - num_trans - number of transparent entries - (PNG_INFO_tRNS) png_get_hIST(png_ptr, info_ptr, &hist); (PNG_INFO_hIST) + hist - histogram of palette (array of png_uint_16) png_get_tIME(png_ptr, info_ptr, &mod_time); + mod_time - time image was last modified (PNG_VALID_tIME) png_get_bKGD(png_ptr, info_ptr, &background); + background - background color (PNG_VALID_bKGD) valid 16-bit red, green and blue values, regardless of color_type num_comments = png_get_text(png_ptr, info_ptr, &text_ptr, &num_text); + num_comments - number of comments + text_ptr - array of png_text holding image comments + text_ptr[i].compression - type of compression used on "text" PNG_TEXT_COMPRESSION_NONE PNG_TEXT_COMPRESSION_zTXt PNG_ITXT_COMPRESSION_NONE PNG_ITXT_COMPRESSION_zTXt + text_ptr[i].key - keyword for comment. Must contain 1-79 characters. + text_ptr[i].text - text comments for current keyword. Can be empty. + text_ptr[i].text_length - length of text string, after decompression, 0 for iTXt + text_ptr[i].itxt_length - length of itxt string, after decompression, 0 for tEXt/zTXt + text_ptr[i].lang - language of comment (empty string for unknown). + text_ptr[i].lang_key - keyword in UTF-8 (empty string for unknown). + Note that the itxt_length, lang, and lang_key members of the text_ptr structure only exist when the library is built with iTXt chunk support. @@ -1479,6 +2171,7 @@ pointer into the info_ptr is returned for any complex types. num_text - number of comments (same as num_comments; you can put NULL here to avoid the duplication) + Note while png_set_text() will accept text, language, and translated keywords that can be NULL pointers, the structure returned by png_get_text will always contain @@ -1487,49 +2180,68 @@ pointer into the info_ptr is returned for any complex types. num_spalettes = png_get_sPLT(png_ptr, info_ptr, &palette_ptr); + + num_spalettes - number of sPLT chunks read. + palette_ptr - array of palette structures holding contents of one or more sPLT chunks read. - num_spalettes - number of sPLT chunks read. png_get_oFFs(png_ptr, info_ptr, &offset_x, &offset_y, &unit_type); + offset_x - positive offset from the left edge of the screen + offset_y - positive offset from the top edge of the screen + unit_type - PNG_OFFSET_PIXEL, PNG_OFFSET_MICROMETER png_get_pHYs(png_ptr, info_ptr, &res_x, &res_y, &unit_type); + res_x - pixels/unit physical resolution in x direction + res_y - pixels/unit physical resolution in x direction + unit_type - PNG_RESOLUTION_UNKNOWN, PNG_RESOLUTION_METER png_get_sCAL(png_ptr, info_ptr, &unit, &width, &height) + unit - physical scale units (an integer) + width - width of a pixel in physical scale units + height - height of a pixel in physical scale units (width and height are doubles) png_get_sCAL_s(png_ptr, info_ptr, &unit, &width, &height) + unit - physical scale units (an integer) + width - width of a pixel in physical scale units + height - height of a pixel in physical scale units (width and height are strings like "2.54") num_unknown_chunks = png_get_unknown_chunks(png_ptr, info_ptr, &unknowns) + unknowns - array of png_unknown_chunk structures holding unknown chunks + unknowns[i].name - name of unknown chunk + unknowns[i].data - data of unknown chunk + unknowns[i].size - size of unknown chunk's data + unknowns[i].location - position of chunk in file The value of "i" corresponds to the order in which the @@ -1541,36 +2253,57 @@ forms: res_x = png_get_x_pixels_per_meter(png_ptr, info_ptr) + res_y = png_get_y_pixels_per_meter(png_ptr, info_ptr) + res_x_and_y = png_get_pixels_per_meter(png_ptr, info_ptr) + res_x = png_get_x_pixels_per_inch(png_ptr, info_ptr) + res_y = png_get_y_pixels_per_inch(png_ptr, info_ptr) + res_x_and_y = png_get_pixels_per_inch(png_ptr, info_ptr) + aspect_ratio = png_get_pixel_aspect_ratio(png_ptr, info_ptr) - (Each of these returns 0 [signifying "unknown"] if + Each of these returns 0 [signifying "unknown"] if the data is not present or if res_x is 0; - res_x_and_y is 0 if res_x != res_y) + res_x_and_y is 0 if res_x != res_y + + Note that because of the way the resolutions are + stored internally, the inch conversions won't + come out to exactly even number. For example, + 72 dpi is stored as 0.28346 pixels/meter, and + when this is retrieved it is 71.9988 dpi, so + be sure to round the returned value appropriately + if you want to display a reasonable-looking result. The data from the oFFs chunk can be retrieved in several convenient forms: x_offset = png_get_x_offset_microns(png_ptr, info_ptr); + y_offset = png_get_y_offset_microns(png_ptr, info_ptr); + x_offset = png_get_x_offset_inches(png_ptr, info_ptr); + y_offset = png_get_y_offset_inches(png_ptr, info_ptr); - (Each of these returns 0 [signifying "unknown" if both + Each of these returns 0 [signifying "unknown" if both x and y are 0] if the data is not present or if the - chunk is present but the unit is the pixel) + chunk is present but the unit is the pixel. The + remark about inexact inch conversions applies here + as well, because a value in inches can't always be + converted to microns and back without some loss + of precision. -For more information, see the png_info definition in png.h and the +For more information, see the PNG specification for chunk contents. Be careful with trusting rowbytes, as some of the transformations could increase the space needed to hold a row (expand, filler, gray_to_rgb, etc.). @@ -1605,17 +2338,20 @@ to handle any special transformations of the image data. The various ways to transform the data will be described in the order that they should occur. This is important, as some of these change the color type and/or bit depth of the data, and some others only work on -certain color types and bit depths. Even though each transformation -checks to see if it has data that it can do something with, you should -make sure to only enable a transformation if it will be valid for the -data. For example, don't swap red and blue on grayscale data. +certain color types and bit depths. + +Transformations you request are ignored if they don't have any meaning for a +particular input data format. However some transformations can have an effect +as a result of a previous transformation. If you specify a contradictory set of +transformations, for example both adding and removing the alpha channel, you +cannot predict the final result. -The colors used for the background and transparency values should be -supplied in the same format/depth as the current image data. They -are stored in the same format/depth as the image data in a bKGD or tRNS -chunk, so this is what libpng expects for this data. The colors are -transformed to keep in sync with the image data when an application -calls the png_read_update_info() routine (see below). +The color used for the transparency values should be supplied in the same +format/depth as the current image data. It is stored in the same format/depth +as the image data in a tRNS chunk, so this is what libpng expects for this data. + +The color used for the background value depends on the need_expand argument as +described below. Data will be decoded into the supplied row buffers packed into bytes unless the library has been told to transform it into another format. @@ -1625,12 +2361,12 @@ byte, unless png_set_packing() is called. 8-bit RGB data will be stored in RGB RGB RGB format unless png_set_filler() or png_set_add_alpha() is called to insert filler bytes, either before or after each RGB triplet. 16-bit RGB data will be returned RRGGBB RRGGBB, with the most significant -byte of the color value first, unless png_set_strip_16() is called to +byte of the color value first, unless png_set_scale_16() is called to transform it to regular RGB RGB triplets, or png_set_filler() or png_set_add alpha() is called to insert filler bytes, either before or after each RRGGBB triplet. Similarly, 8-bit or 16-bit grayscale data can -be modified with -png_set_filler(), png_set_add_alpha(), or png_set_strip_16(). +be modified with png_set_filler(), png_set_add_alpha(), png_set_strip_16(), +or png_set_scale_16(). The following code transforms grayscale images of less than 8 to 8 bits, changes paletted images to RGB, and adds a full alpha channel if there is @@ -1641,13 +2377,13 @@ viewing application that wishes to treat all images in the same way. if (color_type == PNG_COLOR_TYPE_PALETTE) png_set_palette_to_rgb(png_ptr); - if (color_type == PNG_COLOR_TYPE_GRAY && - bit_depth < 8) png_set_expand_gray_1_2_4_to_8(png_ptr); - if (png_get_valid(png_ptr, info_ptr, PNG_INFO_tRNS)) png_set_tRNS_to_alpha(png_ptr); -These three functions are actually aliases for png_set_expand(), added + if (color_type == PNG_COLOR_TYPE_GRAY && + bit_depth < 8) png_set_expand_gray_1_2_4_to_8(png_ptr); + +The first two functions are actually aliases for png_set_expand(), added in libpng version 1.0.4, with the function names expanded to improve code readability. In some future version they may actually do different things. @@ -1655,56 +2391,84 @@ things. As of libpng version 1.2.9, png_set_expand_gray_1_2_4_to_8() was added. It expands the sample depth without changing tRNS to alpha. -As of libpng version 1.4.0, not all possible expansions are supported. +As of libpng version 1.5.2, png_set_expand_16() was added. It behaves as +png_set_expand(), however, the resultant channels have 16 bits rather than 8. +Use this when the output color or gray channels are made linear to avoid fairly +severe accuracy loss. + + if (bit_depth < 16) + png_set_expand_16(png_ptr); + +PNG can have files with 16 bits per channel. If you only can handle +8 bits per channel, this will strip the pixels down to 8-bit. + + if (bit_depth == 16) + png_set_scale_16(png_ptr); + +If you need to process the alpha channel on the image separately from the image +data (for example if you convert it to a bitmap mask) it is possible to have +libpng strip the channel leaving just RGB or gray data: + + if (color_type & PNG_COLOR_MASK_ALPHA) + png_set_strip_alpha(png_ptr); + +If you strip the alpha channel you need to find some other way of dealing with +the information. If, instead, you want to convert the image to an opaque +version with no alpha channel use png_set_background; see below. + +As of libpng version 1.5.2, almost all useful expansions are supported, the +major ommissions are conversion of grayscale to indexed images (which can be +done trivially in the application) and conversion of indexed to grayscale (which +can be done by a trivial manipulation of the palette.) In the following table, the 01 means grayscale with depth<8, 31 means indexed with depth<8, other numerals represent the color type, "T" means the tRNS chunk is present, A means an alpha channel is present, and O means tRNS or alpha is present but all pixels in the image are opaque. - FROM 01 31 0 0T 0O 2 2T 2O 3 3T 3O 4A 4O 6A 6O + FROM 01 31 0 0T 0O 2 2T 2O 3 3T 3O 4A 4O 6A 6O TO - 01 - - 31 - - 0 1 - - 0T - - 0O - - 2 GX - - 2T - - 2O - - 3 1 - - 3T - - 3O - - 4A T - - 4O - - 6A GX TX TX - - 6O GX TX - + 01 - [G] - - - - - - - - - - - - - + 31 [Q] Q [Q] [Q] [Q] Q Q Q Q Q Q [Q] [Q] Q Q + 0 1 G + . . G G G G G G B B GB GB + 0T lt Gt t + . Gt G G Gt G G Bt Bt GBt GBt + 0O lt Gt t . + Gt Gt G Gt Gt G Bt Bt GBt GBt + 2 C P C C C + . . C - - CB CB B B + 2T Ct - Ct C C t + t - - - CBt CBt Bt Bt + 2O Ct - Ct C C t t + - - - CBt CBt Bt Bt + 3 [Q] p [Q] [Q] [Q] Q Q Q + . . [Q] [Q] Q Q + 3T [Qt] p [Qt][Q] [Q] Qt Qt Qt t + t [Qt][Qt] Qt Qt + 3O [Qt] p [Qt][Q] [Q] Qt Qt Qt t t + [Qt][Qt] Qt Qt + 4A lA G A T T GA GT GT GA GT GT + BA G GBA + 4O lA GBA A T T GA GT GT GA GT GT BA + GBA G + 6A CA PA CA C C A T tT PA P P C CBA + BA + 6O CA PBA CA C C A tT T PA P P CBA C BA + Within the matrix, + "+" identifies entries where 'from' and 'to' are the same. "-" means the transformation is not supported. + "." means nothing is necessary (a tRNS chunk can just be ignored). + "t" means the transformation is obtained by png_set_tRNS. + "A" means the transformation is obtained by png_set_add_alpha(). "X" means the transformation is obtained by png_set_expand(). "1" means the transformation is obtained by - png_set_expand_gray_1_2_4_to_8 - "G" means the transformation is obtained by - png_set_gray_to_rgb(). + png_set_expand_gray_1_2_4_to_8() (and by png_set_expand() if there + is no transparency in the original or the final format). + "C" means the transformation is obtained by png_set_gray_to_rgb(). + "G" means the transformation is obtained by png_set_rgb_to_gray(). "P" means the transformation is obtained by png_set_expand_palette_to_rgb(). - "T" means the transformation is obtained by - png_set_tRNS_to_alpha(). - -PNG can have files with 16 bits per channel. If you only can handle -8 bits per channel, this will strip the pixels down to 8 bit. - - if (bit_depth == 16) - png_set_strip_16(png_ptr); - -If, for some reason, you don't need the alpha channel on an image, -and you want to remove it rather than combining it with the background -(but the image author certainly had in mind that you *would* combine -it with the background, so that's what you should probably do): - - if (color_type & PNG_COLOR_MASK_ALPHA) - png_set_strip_alpha(png_ptr); + "p" means the transformation is obtained by png_set_packing(). + "Q" means the transformation is obtained by png_set_quantize(). + "T" means the transformation is obtained by png_set_tRNS_to_alpha(). + "B" means the transformation is obtained by png_set_background(), or + png_strip_alpha(). + +When an entry has multiple transforms listed all are required to cause the +right overall transformation. When two transforms are separated by a comma +either will do the job. When transforms are enclosed in [] the transform should +do the job but this is currently unimplemented - a different format will result +if the suggested transformations are used. In PNG files, the alpha channel in an image is the level of opacity. If you need the alpha channel in an image to @@ -1721,7 +2485,7 @@ files. This code expands to 1 pixel per byte without changing the values of the pixels: if (bit_depth < 8) - png_set_packing(png_ptr); + png_set_packing(png_ptr); PNG files have possible bit depths of 1, 2, 4, 8, and 16. All pixels stored in a PNG image have been "scaled" or "shifted" up to the next @@ -1733,20 +2497,20 @@ image. This call reduces the pixels back down to the original bit depth: png_color_8p sig_bit; if (png_get_sBIT(png_ptr, info_ptr, &sig_bit)) - png_set_shift(png_ptr, sig_bit); + png_set_shift(png_ptr, sig_bit); PNG files store 3-color pixels in red, green, blue order. This code changes the storage of the pixels to blue, green, red: if (color_type == PNG_COLOR_TYPE_RGB || color_type == PNG_COLOR_TYPE_RGB_ALPHA) - png_set_bgr(png_ptr); + png_set_bgr(png_ptr); PNG files store RGB pixels packed into 3 or 6 bytes. This code expands them into 4 or 8 bytes for windowing systems that need them in this format: if (color_type == PNG_COLOR_TYPE_RGB) - png_set_filler(png_ptr, filler, PNG_FILLER_BEFORE); + png_set_filler(png_ptr, filler, PNG_FILLER_BEFORE); where "filler" is the 8 or 16-bit number to fill with, and the location is either PNG_FILLER_BEFORE or PNG_FILLER_AFTER, depending upon whether @@ -1759,8 +2523,8 @@ Note that png_set_filler() does not change the color type. If you want to do that, you can add a true alpha channel with if (color_type == PNG_COLOR_TYPE_RGB || - color_type == PNG_COLOR_TYPE_GRAY) - png_set_add_alpha(png_ptr, filler, PNG_FILLER_AFTER); + color_type == PNG_COLOR_TYPE_GRAY) + png_set_add_alpha(png_ptr, filler, PNG_FILLER_AFTER); where "filler" contains the alpha value to assign to each pixel. This function was added in libpng-1.2.7. @@ -1769,152 +2533,159 @@ If you are reading an image with an alpha channel, and you need the data as ARGB instead of the normal PNG format RGBA: if (color_type == PNG_COLOR_TYPE_RGB_ALPHA) - png_set_swap_alpha(png_ptr); + png_set_swap_alpha(png_ptr); For some uses, you may want a grayscale image to be represented as RGB. This code will do that conversion: if (color_type == PNG_COLOR_TYPE_GRAY || color_type == PNG_COLOR_TYPE_GRAY_ALPHA) - png_set_gray_to_rgb(png_ptr); + png_set_gray_to_rgb(png_ptr); Conversely, you can convert an RGB or RGBA image to grayscale or grayscale with alpha. if (color_type == PNG_COLOR_TYPE_RGB || color_type == PNG_COLOR_TYPE_RGB_ALPHA) - png_set_rgb_to_gray_fixed(png_ptr, error_action, - int red_weight, int green_weight); + png_set_rgb_to_gray(png_ptr, error_action, double red_weight, + double green_weight); error_action = 1: silently do the conversion + error_action = 2: issue a warning if the original image has any pixel where red != green or red != blue + error_action = 3: issue an error and abort the conversion if the original image has any pixel where red != green or red != blue - red_weight: weight of red component times 100000 - green_weight: weight of green component times 100000 + red_weight: weight of red component + + green_weight: weight of green component If either weight is negative, default - weights (21268, 71514) are used. + weights are used. + +In the corresponding fixed point API the red_weight and green_weight values are +simply scaled by 100,000: + + png_set_rgb_to_gray(png_ptr, error_action, png_fixed_point red_weight, + png_fixed_point green_weight); If you have set error_action = 1 or 2, you can later check whether the image really was gray, after processing the image rows, with the png_get_rgb_to_gray_status(png_ptr) function. It will return a png_byte that is zero if the image was gray or -1 if there were any non-gray pixels. bKGD and sBIT data +1 if there were any non-gray pixels. Background and sBIT data will be silently converted to grayscale, using the green channel -data, regardless of the error_action setting. - -With red_weight+green_weight<=100000, -the normalized graylevel is computed: +data for sBIT, regardless of the error_action setting. - int rw = red_weight * 65536; - int gw = green_weight * 65536; - int bw = 65536 - (rw + gw); - gray = (rw*red + gw*green + bw*blue)/65536; +The default values come from the PNG file cHRM chunk if present, otherwise the +defaults correspond to the ITU-R recommendation 709, and also the sRGB color +space, as recommended in the Charles Poynton's Colour FAQ, +<http://www.poynton.com/>, in section 9: -The default values approximate those recommended in the Charles -Poynton's Color FAQ, <http://www.inforamp.net/~poynton/> -Copyright (c) 1998-01-04 Charles Poynton <poynton at inforamp.net> + <http://www.poynton.com/notes/colour_and_gamma/ColorFAQ.html#RTFToC9> Y = 0.212671 * R + 0.715160 * G + 0.072169 * B -Libpng approximates this with - - Y = 0.21268 * R + 0.7151 * G + 0.07217 * B - -which can be expressed with integers as - - Y = (6969 * R + 23434 * G + 2365 * B)/32768 - The calculation is done in a linear colorspace, if the image gamma -is known. +can be determined. -If you have a grayscale and you are using png_set_expand_depth(), -png_set_expand(), or png_set_gray_to_rgb to change to truecolor or to -a higher bit-depth, you must either supply the background color as a gray -value at the original file bit-depth (need_expand = 1) or else supply the -background color as an RGB triplet at the final, expanded bit depth -(need_expand = 0). Similarly, if you are reading a paletted image, you -must either supply the background color as a palette index (need_expand = 1) -or as an RGB triplet that may or may not be in the palette (need_expand = 0). +The png_set_background() function has been described already, it tells libpng to +composite images with alpha or simple transparency against the supplied +background color. For compatibility with versions of libpng earlier than +libpng-1.5.4 it is recommended that you call the function after reading the file +header, even if you don't want to use the color in a bKGD chunk, if one exists. + +If the PNG file contains a bKGD chunk (PNG_INFO_bKGD valid), +you may use this color, or supply another color more suitable for +the current display (e.g., the background color from a web page). You +need to tell libpng how the color is represented, both the format of the +component values in the color (the number of bits) and the gamme encoding of the +color. The function takes two arguments, background_gamma_mode and need_expand +to convey this information, however only two combinations are like to be useful: png_color_16 my_background; png_color_16p image_background; if (png_get_bKGD(png_ptr, info_ptr, &image_background)) - png_set_background(png_ptr, image_background, - PNG_BACKGROUND_GAMMA_FILE, 1, 1.0); + png_set_background(png_ptr, image_background, + PNG_BACKGROUND_GAMMA_FILE, 1/*needs to be expanded*/, 1); else - png_set_background(png_ptr, &my_background, - PNG_BACKGROUND_GAMMA_SCREEN, 0, 1.0); + png_set_background(png_ptr, &my_background, + PNG_BACKGROUND_GAMMA_SCREEN, 0/*do not expand*/, 1); -The png_set_background() function tells libpng to composite images -with alpha or simple transparency against the supplied background -color. If the PNG file contains a bKGD chunk (PNG_INFO_bKGD valid), -you may use this color, or supply another color more suitable for -the current display (e.g., the background color from a web page). You -need to tell libpng whether the color is in the gamma space of the -display (PNG_BACKGROUND_GAMMA_SCREEN for colors you supply), the file -(PNG_BACKGROUND_GAMMA_FILE for colors from the bKGD chunk), or one -that is neither of these gammas (PNG_BACKGROUND_GAMMA_UNIQUE - I don't -know why anyone would use this, but it's here). - -To properly display PNG images on any kind of system, the application needs -to know what the display gamma is. Ideally, the user will know this, and -the application will allow them to set it. One method of allowing the user -to set the display gamma separately for each system is to check for a -SCREEN_GAMMA or DISPLAY_GAMMA environment variable, which will hopefully be -correctly set. - -Note that display_gamma is the overall gamma correction required to produce -pleasing results, which depends on the lighting conditions in the surrounding -environment. In a dim or brightly lit room, no compensation other than -the physical gamma exponent of the monitor is needed, while in a dark room -a slightly smaller exponent is better. - - double gamma, screen_gamma; - - if (/* We have a user-defined screen - gamma value */) - { - screen_gamma = user_defined_screen_gamma; - } - /* One way that applications can share the same - screen gamma value */ - else if ((gamma_str = getenv("SCREEN_GAMMA")) - != NULL) - { - screen_gamma = (double)atof(gamma_str); - } - /* If we don't have another value */ - else - { - screen_gamma = 2.2; /* A good guess for a - PC monitor in a bright office or a dim room */ - screen_gamma = 2.0; /* A good guess for a - PC monitor in a dark room */ - screen_gamma = 1.7 or 1.0; /* A good - guess for Mac systems */ - } -The png_set_gamma() function handles gamma transformations of the data. -Pass both the file gamma and the current screen_gamma. If the file does -not have a gamma value, you can pass one anyway if you have an idea what -it is (usually 0.45455 is a good guess for GIF images on PCs). Note -that file gammas are inverted from screen gammas. See the discussions -on gamma in the PNG specification for an excellent description of what -gamma is, and why all applications should support it. It is strongly -recommended that PNG viewers support gamma correction. - - if (png_get_gAMA(png_ptr, info_ptr, &gamma)) - png_set_gamma(png_ptr, screen_gamma, gamma); +The second call was described above - my_background is in the format of the +final, display, output produced by libpng. Because you now know the format of +the PNG it is possible to avoid the need to choose either 8-bit or 16-bit +output and to retain palette images (the palette colors will be modified +appropriately and the tRNS chunk removed.) However, if you are doing this, +take great care not to ask for transformations without checking first that +they apply! + +In the first call the background color has the original bit depth and color type +of the PNG file. So, for palette images the color is supplied as a palette +index and for low bit greyscale images the color is a reduced bit value in +image_background->gray. + +If you didn't call png_set_gamma() before reading the file header, for example +if you need your code to remain compatible with older versions of libpng prior +to libpng-1.5.4, this is the place to call it. + +Do not call it if you called png_set_alpha_mode(); doing so will damage the +settings put in place by png_set_alpha_mode(). (If png_set_alpha_mode() is +supported then you can certainly do png_set_gamma() before reading the PNG +header.) + +This API unconditionally sets the screen and file gamma values, so it will +override the value in the PNG file unless it is called before the PNG file +reading starts. For this reason you must always call it with the PNG file +value when you call it in this position: + + if (png_get_gAMA(png_ptr, info_ptr, &file_gamma)) + png_set_gamma(png_ptr, screen_gamma, file_gamma); + else png_set_gamma(png_ptr, screen_gamma, 0.45455); +If you need to reduce an RGB file to a paletted file, or if a paletted +file has more entries then will fit on your screen, png_set_quantize() +will do that. Note that this is a simple match quantization that merely +finds the closest color available. This should work fairly well with +optimized palettes, but fairly badly with linear color cubes. If you +pass a palette that is larger then maximum_colors, the file will +reduce the number of colors in the palette so it will fit into +maximum_colors. If there is a histogram, it will use it to make +more intelligent choices when reducing the palette. If there is no +histogram, it may not do as good a job. + + if (color_type & PNG_COLOR_MASK_COLOR) + { + if (png_get_valid(png_ptr, info_ptr, + PNG_INFO_PLTE)) + { + png_uint_16p histogram = NULL; + + png_get_hIST(png_ptr, info_ptr, + &histogram); + png_set_quantize(png_ptr, palette, num_palette, + max_screen_colors, histogram, 1); + } + + else + { + png_color std_color_cube[MAX_SCREEN_COLORS] = + { ... colors ... }; + + png_set_quantize(png_ptr, std_color_cube, + MAX_SCREEN_COLORS, MAX_SCREEN_COLORS, + NULL,0); + } + } + PNG files describe monochrome as black being zero and white being one. The following code will reverse this (make black be one and white be zero): @@ -1925,16 +2696,16 @@ zero): This function can also be used to invert grayscale and gray-alpha images: if (color_type == PNG_COLOR_TYPE_GRAY || - color_type == PNG_COLOR_TYPE_GRAY_ALPHA) + color_type == PNG_COLOR_TYPE_GRAY_ALPHA) png_set_invert_mono(png_ptr); -PNG files store 16 bit pixels in network byte order (big-endian, +PNG files store 16-bit pixels in network byte order (big-endian, ie. most significant bits first). This code changes the storage to the other way (little-endian, i.e. least significant bits first, the way PCs store them): if (bit_depth == 16) - png_set_swap(png_ptr); + png_set_swap(png_ptr); If you are using packed-pixel images (1, 2, or 4 bits/pixel), and you need to change the order the pixels are packed into bytes, you can use: @@ -1947,15 +2718,36 @@ the existing ones meets your needs. This is done by setting a callback with png_set_read_user_transform_fn(png_ptr, - read_transform_fn); + read_transform_fn); You must supply the function - void read_transform_fn(png_ptr ptr, row_info_ptr - row_info, png_bytep data) + void read_transform_fn(png_structp png_ptr, png_row_infop + row_info, png_bytep data) See pngtest.c for a working example. Your function will be called -after all of the other transformations have been processed. +after all of the other transformations have been processed. Take care with +interlaced images if you do the interlace yourself - the width of the row is the +width in 'row_info', not the overall image width. + +If supported libpng provides two information routines that you can use to find +where you are in processing the image: + + png_get_current_pass_number(png_structp png_ptr); + png_get_current_row_number(png_structp png_ptr); + +Don't try using these outside a transform callback - firstly they are only +supported if user transforms are supported, secondly they may well return +unexpected results unless the row is actually being processed at the moment they +are called. + +With interlaced +images the value returned is the row in the input sub-image image. Use +PNG_ROW_FROM_PASS_ROW(row, pass) and PNG_COL_FROM_PASS_COL(col, pass) to +find the output pixel (x,y) given an interlaced sub-image pixel (row,col,pass). + +The discussion of interlace handling above contains more information on how to +use these values. You can also set up a pointer to a user structure for use by your callback function, and you can inform libpng that your transform @@ -1963,7 +2755,7 @@ function will change the number of channels or bit depth with the function png_set_user_transform_info(png_ptr, user_ptr, - user_depth, user_channels); + user_depth, user_channels); The user's application, not libpng, is responsible for allocating and freeing any memory required for the user structure. @@ -1972,7 +2764,7 @@ You can retrieve the pointer via the function png_get_user_transform_ptr(). For example: voidp read_user_transform_ptr = - png_get_user_transform_ptr(png_ptr); + png_get_user_transform_ptr(png_ptr); The last thing to handle is interlacing; this is covered in detail below, but you must call the function here if you want libpng to handle expansion @@ -1997,6 +2789,15 @@ are allocating one large chunk, you will need to build an array of pointers to each row, as it will be needed for some of the functions below. +Remember: Before you call png_read_update_info(), the png_get_ +functions return the values corresponding to the original PNG image. +After you call png_read_update_info the values refer to the image +that libpng will output. Consequently you must call all the png_set_ +functions before you call png_read_update_info(). This is particularly +important for png_set_interlace_handling() - if you are going to call +png_read_update_info() you must call png_set_interlace_handling() before +it unless you want to receive interlaced output. + .SS Reading image data After you've allocated memory, you can read the image data. @@ -2006,9 +2807,10 @@ call png_read_image() and libpng will read in all the image data and put it in the memory area supplied. You will need to pass in an array of pointers to each row. -This function automatically handles interlacing, so you don't need -to call png_set_interlace_handling() or call this function multiple -times, or any of that other stuff necessary with png_read_rows(). +This function automatically handles interlacing, so you don't +need to call png_set_interlace_handling() (unless you call +png_read_update_info()) or call this function multiple times, or any +of that other stuff necessary with png_read_rows(). png_read_image(png_ptr, row_pointers); @@ -2023,7 +2825,7 @@ use png_read_rows() instead. If there is no interlacing (check interlace_type == PNG_INTERLACE_NONE), this is simple: png_read_rows(png_ptr, row_pointers, NULL, - number_of_rows); + number_of_rows); where row_pointers is the same as in the png_read_image() call. @@ -2035,13 +2837,15 @@ a single row_pointer instead of an array of row_pointers: If the file is interlaced (interlace_type != 0 in the IHDR chunk), things get somewhat harder. The only current (PNG Specification version 1.2) -interlacing type for PNG is (interlace_type == PNG_INTERLACE_ADAM7) -is a somewhat complicated 2D interlace scheme, known as Adam7, that +interlacing type for PNG is (interlace_type == PNG_INTERLACE_ADAM7); +a somewhat complicated 2D interlace scheme, known as Adam7, that breaks down an image into seven smaller images of varying size, based -on an 8x8 grid. +on an 8x8 grid. This number is defined (from libpng 1.5) as +PNG_INTERLACE_ADAM7_PASSES in png.h libpng can fill out those images or it can give them to you "as is". -If you want them filled out, there are two ways to do that. The one +It is almost always better to have libpng handle the interlacing for you. +If you want the images filled out, there are two ways to do that. The one mentioned in the PNG specification is to expand each pixel to cover those pixels that have not been read yet (the "rectangle" method). This results in a blocky image for the first pass, which gradually @@ -2051,37 +2855,20 @@ rest of the image remaining whatever colors they were initialized to before the start of the read. The first method usually looks better, but tends to be slower, as there are more pixels to put in the rows. -If you don't want libpng to handle the interlacing details, just call -png_read_rows() seven times to read in all seven images. Each of the -images is a valid image by itself, or they can all be combined on an -8x8 grid to form a single image (although if you intend to combine them -you would be far better off using the libpng interlace handling). - -The first pass will return an image 1/8 as wide as the entire image -(every 8th column starting in column 0) and 1/8 as high as the original -(every 8th row starting in row 0), the second will be 1/8 as wide -(starting in column 4) and 1/8 as high (also starting in row 0). The -third pass will be 1/4 as wide (every 4th pixel starting in column 0) and -1/8 as high (every 8th row starting in row 4), and the fourth pass will -be 1/4 as wide and 1/4 as high (every 4th column starting in column 2, -and every 4th row starting in row 0). The fifth pass will return an -image 1/2 as wide, and 1/4 as high (starting at column 0 and row 2), -while the sixth pass will be 1/2 as wide and 1/2 as high as the original -(starting in column 1 and row 0). The seventh and final pass will be as -wide as the original, and 1/2 as high, containing all of the odd -numbered scanlines. Phew! - -If you want libpng to expand the images, call this before calling -png_start_read_image() or png_read_update_info(): +If, as is likely, you want libpng to expand the images, call this before +calling png_start_read_image() or png_read_update_info(): if (interlace_type == PNG_INTERLACE_ADAM7) - number_of_passes + number_of_passes = png_set_interlace_handling(png_ptr); -This will return the number of passes needed. Currently, this -is seven, but may change if another interlace type is added. -This function can be called even if the file is not interlaced, -where it will return one pass. +This will return the number of passes needed. Currently, this is seven, +but may change if another interlace type is added. This function can be +called even if the file is not interlaced, where it will return one pass. +You then need to read the whole image 'number_of_passes' times. Each time +will distribute the pixels from the current pass to the correct place in +the output image, so you need to supply the same rows to png_read_rows in +each pass. If you are not going to display the image after each pass, but are going to wait until the entire image is read in, use the sparkle @@ -2098,14 +2885,104 @@ not the data. Each pass only writes the pixels appropriate for that pass, and assumes the data from previous passes is still valid. png_read_rows(png_ptr, row_pointers, NULL, - number_of_rows); + number_of_rows); If you only want the first effect (the rectangles), do the same as before except pass the row buffer in the third parameter, and leave the second parameter NULL. png_read_rows(png_ptr, NULL, row_pointers, - number_of_rows); + number_of_rows); + +If you don't want libpng to handle the interlacing details, just call +png_read_rows() PNG_INTERLACE_ADAM7_PASSES times to read in all the images. +Each of the images is a valid image by itself, however you will almost +certainly need to distribute the pixels from each sub-image to the +correct place. This is where everything gets very tricky. + +If you want to retrieve the separate images you must pass the correct +number of rows to each successive call of png_read_rows(). The calculation +gets pretty complicated for small images, where some sub-images may +not even exist because either their width or height ends up zero. +libpng provides two macros to help you in 1.5 and later versions: + + png_uint_32 width = PNG_PASS_COLS(image_width, pass_number); + png_uint_32 height = PNG_PASS_ROWS(image_height, pass_number); + +Respectively these tell you the width and height of the sub-image +corresponding to the numbered pass. 'pass' is in in the range 0 to 6 - +this can be confusing because the specification refers to the same passes +as 1 to 7! Be careful, you must check both the width and height before +calling png_read_rows() and not call it for that pass if either is zero. + +You can, of course, read each sub-image row by row. If you want to +produce optimal code to make a pixel-by-pixel transformation of an +interlaced image this is the best approach; read each row of each pass, +transform it, and write it out to a new interlaced image. + +If you want to de-interlace the image yourself libpng provides further +macros to help that tell you where to place the pixels in the output image. +Because the interlacing scheme is rectangular - sub-image pixels are always +arranged on a rectangular grid - all you need to know for each pass is the +starting column and row in the output image of the first pixel plus the +spacing between each pixel. As of libpng 1.5 there are four macros to +retrieve this information: + + png_uint_32 x = PNG_PASS_START_COL(pass); + png_uint_32 y = PNG_PASS_START_ROW(pass); + png_uint_32 xStep = 1U << PNG_PASS_COL_SHIFT(pass); + png_uint_32 yStep = 1U << PNG_PASS_ROW_SHIFT(pass); + +These allow you to write the obvious loop: + + png_uint_32 input_y = 0; + png_uint_32 output_y = PNG_PASS_START_ROW(pass); + + while (output_y < output_image_height) + { + png_uint_32 input_x = 0; + png_uint_32 output_x = PNG_PASS_START_COL(pass); + + while (output_x < output_image_width) + { + image[output_y][output_x] = + subimage[pass][input_y][input_x++]; + + output_x += xStep; + } + + ++input_y; + output_y += yStep; + } + +Notice that the steps between successive output rows and columns are +returned as shifts. This is possible because the pixels in the subimages +are always a power of 2 apart - 1, 2, 4 or 8 pixels - in the original +image. In practice you may need to directly calculate the output coordinate +given an input coordinate. libpng provides two further macros for this +purpose: + + png_uint_32 output_x = PNG_COL_FROM_PASS_COL(input_x, pass); + png_uint_32 output_y = PNG_ROW_FROM_PASS_ROW(input_y, pass); + +Finally a pair of macros are provided to tell you if a particular image +row or column appears in a given pass: + + int col_in_pass = PNG_COL_IN_INTERLACE_PASS(output_x, pass); + int row_in_pass = PNG_ROW_IN_INTERLACE_PASS(output_y, pass); + +Bear in mind that you will probably also need to check the width and height +of the pass in addition to the above to be sure the pass even exists! + +With any luck you are convinced by now that you don't want to do your own +interlace handling. In reality normally the only good reason for doing this +is if you are processing PNG files on a pixel-by-pixel basis and don't want +to load the whole file into memory when it is interlaced. + +libpng includes a test program, pngvalid, that illustrates reading and +writing of interlaced images. If you can't get interlacing to work in your +code and don't want to leave it to libpng (the recommended approach) see +how pngvalid.c does it. .SS Finishing a sequential read @@ -2114,19 +2991,44 @@ low-level interface, you can finish reading the file. If you are interested in comments or time, which may be stored either before or after the image data, you should pass the separate png_info struct if you want to keep the comments from before and after the image -separate. If you are not interested, you can pass NULL. +separate. + + png_infop end_info = png_create_info_struct(png_ptr); + + if (!end_info) + { + png_destroy_read_struct(&png_ptr, &info_ptr, + (png_infopp)NULL); + return (ERROR); + } png_read_end(png_ptr, end_info); +If you are not interested, you should still call png_read_end() +but you can pass NULL, avoiding the need to create an end_info structure. + + png_read_end(png_ptr, (png_infop)NULL); + +If you don't call png_read_end(), then your file pointer will be +left pointing to the first chunk after the last IDAT, which is probably +not what you want if you expect to read something beyond the end of +the PNG datastream. + When you are done, you can free all memory allocated by libpng like this: png_destroy_read_struct(&png_ptr, &info_ptr, &end_info); +or, if you didn't create an end_info structure, + + png_destroy_read_struct(&png_ptr, &info_ptr, + (png_infopp)NULL); + It is also possible to individually free the info_ptr members that point to libpng-allocated storage with the following function: png_free_data(png_ptr, info_ptr, mask, seq) + mask - identifies data to be freed, a mask containing the bitwise OR of one or more of @@ -2136,6 +3038,7 @@ point to libpng-allocated storage with the following function: PNG_FREE_SCAL, PNG_FREE_SPLT, PNG_FREE_TEXT, PNG_FREE_UNKN, or simply PNG_FREE_ALL + seq - sequence number of item to be freed (-1 for all items) @@ -2153,13 +3056,15 @@ or so that it will free data that was allocated by the user with png_malloc() or png_zalloc() and passed in via a png_set_*() function, with png_data_freer(png_ptr, info_ptr, freer, mask) - mask - which data elements are affected - same choices as in png_free_data() + freer - one of PNG_DESTROY_WILL_FREE_DATA PNG_SET_WILL_FREE_DATA PNG_USER_WILL_FREE_DATA + mask - which data elements are affected + same choices as in png_free_data() + This function only affects data that has already been allocated. You can call this function after reading the PNG data but before calling any png_set_*() functions, to control whether the user or the png_set_*() @@ -2188,6 +3093,7 @@ it frees. If you need to turn the flag off for a chunk that was freed by your application instead of by libpng, you can use png_set_invalid(png_ptr, info_ptr, mask); + mask - identifies the chunks to be made invalid, containing the bitwise OR of one or more of @@ -2227,21 +3133,24 @@ png_infop info_ptr; png_ptr = png_create_read_struct (PNG_LIBPNG_VER_STRING, (png_voidp)user_error_ptr, user_error_fn, user_warning_fn); + if (!png_ptr) return (ERROR); + info_ptr = png_create_info_struct(png_ptr); + if (!info_ptr) { - png_destroy_read_struct(&png_ptr, (png_infopp)NULL, - (png_infopp)NULL); - return (ERROR); + png_destroy_read_struct(&png_ptr, + (png_infopp)NULL, (png_infopp)NULL); + return (ERROR); } if (setjmp(png_jmpbuf(png_ptr))) { - png_destroy_read_struct(&png_ptr, &info_ptr, - (png_infopp)NULL); - return (ERROR); + png_destroy_read_struct(&png_ptr, &info_ptr, + (png_infopp)NULL); + return (ERROR); } /* This one's new. You can provide functions @@ -2273,9 +3182,9 @@ png_infop info_ptr; { if (setjmp(png_jmpbuf(png_ptr))) { - png_destroy_read_struct(&png_ptr, &info_ptr, + png_destroy_read_struct(&png_ptr, &info_ptr, (png_infopp)NULL); - return (ERROR); + return (ERROR); } /* This one's new also. Simply give it a chunk @@ -2292,6 +3201,12 @@ png_infop info_ptr; so there. */ png_process_data(png_ptr, info_ptr, buffer, length); + + /* At this point you can call png_process_data_skip if + you want to handle data the library will skip yourself; + it simply returns the number of bytes to skip (and stops + libpng skipping that number of bytes on the next + png_process_data call). return 0; } @@ -2312,6 +3227,19 @@ png_infop info_ptr; any). You may start getting rows before png_process_data() returns, so this is your last chance to prepare for that. + + This is where you turn on interlace handling, + assuming you don't want to do it yourself. + + If you need to you can stop the processing of + your original input data at this point by calling + png_process_data_pause. This returns the number + of unprocessed bytes from the last png_process_data + call - it is up to you to ensure that the next call + sees these bytes again. If you don't want to bother + with this you can get libpng to cache the unread + bytes by setting the 'save' parameter (see png.h) but + then libpng will have to copy the data internally. */ } @@ -2332,14 +3260,22 @@ png_infop info_ptr; supplying them because it may make your life easier. - For the non-NULL rows of interlaced images, + If you did not turn on interlace handling then + the callback is called for each row of each + sub-image when the image is interlaced. In this + case 'row_num' is the row in the sub-image, not + the row in the output image as it is in all other + cases. + + For the non-NULL rows of interlaced images when + you have switched on libpng interlace handling, you must call png_progressive_combine_row() passing in the row and the old row. You can call this function for NULL rows (it will just return) and for non-interlaced images (it just does the memcpy for you) if it will make the code easier. Thus, you can just do this for - all cases: + all cases if you switch on interlace handling; */ png_progressive_combine_row(png_ptr, old_row, @@ -2353,6 +3289,9 @@ png_infop info_ptr; for interlaced images), you will have to pass the current row, and the function will combine the old row and the new row. + + You can also call png_process_data_pause in this + callback - see above. */ } @@ -2387,10 +3326,9 @@ using the standard I/O functions, you will need to replace them with custom writing functions. See the discussion under Customizing libpng. FILE *fp = fopen(file_name, "wb"); + if (!fp) - { return (ERROR); - } Next, png_struct and png_info need to be allocated and initialized. As these can be both relatively large, you may not want to store these @@ -2403,6 +3341,7 @@ both "png_ptr"; you can call them anything you like, such as png_structp png_ptr = png_create_write_struct (PNG_LIBPNG_VER_STRING, (png_voidp)user_error_ptr, user_error_fn, user_warning_fn); + if (!png_ptr) return (ERROR); @@ -2410,7 +3349,7 @@ both "png_ptr"; you can call them anything you like, such as if (!info_ptr) { png_destroy_write_struct(&png_ptr, - (png_infopp)NULL); + (png_infopp)NULL); return (ERROR); } @@ -2436,7 +3375,7 @@ section below for more information on the libpng error handling. if (setjmp(png_jmpbuf(png_ptr))) { - png_destroy_write_struct(&png_ptr, &info_ptr); + png_destroy_write_struct(&png_ptr, &info_ptr); fclose(fp); return (ERROR); } @@ -2444,9 +3383,13 @@ section below for more information on the libpng error handling. return; If you would rather avoid the complexity of setjmp/longjmp issues, -you can compile libpng with PNG_SETJMP_NOT_SUPPORTED, in which case +you can compile libpng with PNG_NO_SETJMP, in which case errors will result in a call to PNG_ABORT() which defaults to abort(). +You can #define PNG_ABORT() to a function that does something +more useful than abort(), as long as your function does not +return. + Now you need to set up the output code. The default for libpng is to use the C function fwrite(). If you use this, you will need to pass a valid FILE * in the function png_init_io(). Be sure that the file is @@ -2471,7 +3414,7 @@ called after each row has been written, which you can use to control a progress meter or the like. It's demonstrated in pngtest.c. You must supply a function - void write_row_callback(png_ptr, png_uint_32 row, + void write_row_callback(png_structp png_ptr, png_uint_32 row, int pass); { /* put your code here */ @@ -2483,6 +3426,20 @@ To inform libpng about your function, use png_set_write_status_fn(png_ptr, write_row_callback); +When this function is called the row has already been completely processed and +it has also been written out. The 'row' and 'pass' refer to the next row to be +handled. For the +non-interlaced case the row that was just handled is simply one less than the +passed in row number, and pass will always be 0. For the interlaced case the +same applies unless the row value is 0, in which case the row just handled was +the last one from one of the preceding passes. Because interlacing may skip a +pass you cannot be sure that the preceding pass is just 'pass-1', if you really +need to know what the last pass is record (row,pass) from the callback and use +the last recorded value each time. + +As with the user transform you can find the output row using the +PNG_ROW_FROM_PASS_ROW macro. + You now have the option of modifying how the compression library will run. The following functions are mainly for testing, but may be useful in some cases, like if you need to write PNG files extremely fast and @@ -2502,7 +3459,8 @@ filter types. /* turn on or off filtering, and/or choose specific filters. You can use either a single PNG_FILTER_VALUE_NAME or the bitwise OR of one - or more PNG_FILTER_NAME masks. */ + or more PNG_FILTER_NAME masks. + */ png_set_filter(png_ptr, 0, PNG_FILTER_NONE | PNG_FILTER_VALUE_NONE | PNG_FILTER_SUB | PNG_FILTER_VALUE_SUB | @@ -2511,11 +3469,10 @@ filter types. PNG_FILTER_PAETH | PNG_FILTER_VALUE_PAETH| PNG_ALL_FILTERS); -If an application -wants to start and stop using particular filters during compression, -it should start out with all of the filters (to ensure that the previous -row of pixels will be stored in case it's needed later), and then add -and remove them after the start of compression. +If an application wants to start and stop using particular filters during +compression, it should start out with all of the filters (to ensure that +the previous row of pixels will be stored in case it's needed later), +and then add and remove them after the start of compression. If you are writing a PNG datastream that is to be embedded in a MNG datastream, the second parameter can be either 0 or 64. @@ -2527,11 +3484,13 @@ which changes how much time zlib spends on trying to compress the image data. See the Compression Library (zlib.h and algorithm.txt, distributed with zlib) for details on the compression levels. - /* set the zlib compression level */ + #include zlib.h + + /* Set the zlib compression level */ png_set_compression_level(png_ptr, Z_BEST_COMPRESSION); - /* set other zlib parameters */ + /* Set other zlib parameters for compressing IDAT */ png_set_compression_mem_level(png_ptr, 8); png_set_compression_strategy(png_ptr, Z_DEFAULT_STRATEGY); @@ -2539,7 +3498,15 @@ with zlib) for details on the compression levels. png_set_compression_method(png_ptr, 8); png_set_compression_buffer_size(png_ptr, 8192) -extern PNG_EXPORT(void,png_set_zbuf_size) + /* Set zlib parameters for text compression + * If you don't call these, the parameters + * fall back on those defined for IDAT chunks + */ + png_set_text_compression_mem_level(png_ptr, 8); + png_set_text_compression_strategy(png_ptr, + Z_DEFAULT_STRATEGY); + png_set_text_compression_window_bits(png_ptr, 15); + png_set_text_compression_method(png_ptr, 8); .SS Setting the contents of info for output @@ -2559,16 +3526,20 @@ Some of the more important parts of the png_info are: png_set_IHDR(png_ptr, info_ptr, width, height, bit_depth, color_type, interlace_type, compression_type, filter_method) + width - holds the width of the image in pixels (up to 2^31). + height - holds the height of the image in pixels (up to 2^31). + bit_depth - holds the bit depth of one of the image channels. (valid values are 1, 2, 4, 8, 16 and depend also on the color_type. See also significant bits (sBIT) below). + color_type - describes which color/alpha channels are present. PNG_COLOR_TYPE_GRAY @@ -2588,8 +3559,10 @@ Some of the more important parts of the png_info are: interlace_type - PNG_INTERLACE_NONE or PNG_INTERLACE_ADAM7 + compression_type - (must be PNG_COMPRESSION_TYPE_DEFAULT) + filter_method - (must be PNG_FILTER_TYPE_DEFAULT or, if you are writing a PNG to be embedded in a MNG datastream, @@ -2607,15 +3580,22 @@ width, height, bit_depth, and color_type must be the same in each call. png_set_PLTE(png_ptr, info_ptr, palette, num_palette); + palette - the palette for the file (array of png_color) num_palette - number of entries in the palette - png_set_gAMA(png_ptr, info_ptr, gamma); - gamma - the gamma the image was created - at (PNG_INFO_gAMA) + png_set_gAMA(png_ptr, info_ptr, file_gamma); + png_set_gAMA_fixed(png_ptr, info_ptr, int_file_gamma); + + file_gamma - the gamma at which the image was + created (PNG_INFO_gAMA) + + int_file_gamma - 100,000 times the gamma at which + the image was created png_set_sRGB(png_ptr, info_ptr, srgb_intent); + srgb_intent - the rendering intent (PNG_INFO_sRGB) The presence of the sRGB chunk means that the pixel @@ -2635,6 +3615,7 @@ width, height, bit_depth, and color_type must be the same in each call. png_set_sRGB_gAMA_and_cHRM(png_ptr, info_ptr, srgb_intent); + srgb_intent - the rendering intent (PNG_INFO_sRGB) The presence of the sRGB chunk means that the pixel @@ -2645,17 +3626,22 @@ width, height, bit_depth, and color_type must be the same in each call. written. png_set_iCCP(png_ptr, info_ptr, name, compression_type, - profile, proflen); - name - The profile name. - compression - The compression type; always - PNG_COMPRESSION_TYPE_BASE for PNG 1.0. - You may give NULL to this argument to - ignore it. - profile - International Color Consortium color - profile data. May contain NULs. - proflen - length of profile data in bytes. + profile, proflen); + + name - The profile name. + + compression_type - The compression type; always + PNG_COMPRESSION_TYPE_BASE for PNG 1.0. + You may give NULL to this argument to + ignore it. + + profile - International Color Consortium color + profile data. May contain NULs. + + proflen - length of profile data in bytes. png_set_sBIT(png_ptr, info_ptr, sig_bit); + sig_bit - the number of significant bits for (PNG_INFO_sBIT) each of the gray, red, green, and blue channels, whichever are @@ -2664,30 +3650,37 @@ width, height, bit_depth, and color_type must be the same in each call. png_set_tRNS(png_ptr, info_ptr, trans_alpha, num_trans, trans_color); + trans_alpha - array of alpha (transparency) entries for palette (PNG_INFO_tRNS) + trans_color - graylevel or color sample values (in order red, green, blue) of the single transparent color for non-paletted images (PNG_INFO_tRNS) + num_trans - number of transparent entries (PNG_INFO_tRNS) png_set_hIST(png_ptr, info_ptr, hist); - (PNG_INFO_hIST) + hist - histogram of palette (array of - png_uint_16) + png_uint_16) (PNG_INFO_hIST) png_set_tIME(png_ptr, info_ptr, mod_time); + mod_time - time image was last modified (PNG_VALID_tIME) png_set_bKGD(png_ptr, info_ptr, background); + background - background color (PNG_VALID_bKGD) png_set_text(png_ptr, info_ptr, text_ptr, num_text); + text_ptr - array of png_text holding image comments + text_ptr[i].compression - type of compression used on "text" PNG_TEXT_COMPRESSION_NONE PNG_TEXT_COMPRESSION_zTXt @@ -2713,6 +3706,7 @@ width, height, bit_depth, and color_type must be the same in each call. png_set_sPLT(png_ptr, info_ptr, &palette_ptr, num_spalettes); + palette_ptr - array of png_sPLT_struct structures to be added to the list of palettes in the info structure. @@ -2721,35 +3715,48 @@ width, height, bit_depth, and color_type must be the same in each call. png_set_oFFs(png_ptr, info_ptr, offset_x, offset_y, unit_type); + offset_x - positive offset from the left edge of the screen + offset_y - positive offset from the top edge of the screen + unit_type - PNG_OFFSET_PIXEL, PNG_OFFSET_MICROMETER png_set_pHYs(png_ptr, info_ptr, res_x, res_y, unit_type); + res_x - pixels/unit physical resolution in x direction + res_y - pixels/unit physical resolution in y direction + unit_type - PNG_RESOLUTION_UNKNOWN, PNG_RESOLUTION_METER png_set_sCAL(png_ptr, info_ptr, unit, width, height) + unit - physical scale units (an integer) + width - width of a pixel in physical scale units + height - height of a pixel in physical scale units (width and height are doubles) png_set_sCAL_s(png_ptr, info_ptr, unit, width, height) + unit - physical scale units (an integer) + width - width of a pixel in physical scale units + height - height of a pixel in physical scale units (width and height are strings like "2.54") png_set_unknown_chunks(png_ptr, info_ptr, &unknowns, num_unknowns) + unknowns - array of png_unknown_chunk structures holding unknown chunks unknowns[i].name - name of unknown chunk @@ -2788,21 +3795,30 @@ Until text gets around 1000 bytes, it is not worth compressing it. After the text has been written out to the file, the compression type is set to PNG_TEXT_COMPRESSION_NONE_WR or PNG_TEXT_COMPRESSION_zTXt_WR, so that it isn't written out again at the end (in case you are calling -png_write_end() with the same struct. +png_write_end() with the same struct). The keywords that are given in the PNG Specification are: Title Short (one line) title or caption for image + Author Name of image's creator + Description Description of image (possibly long) + Copyright Copyright notice + Creation Time Time of original image creation (usually RFC 1123 format, see below) + Software Software used to create the image + Disclaimer Legal disclaimer + Warning Warning of nature of content + Source Device used to create the image + Comment Miscellaneous comment; conversion from other image format @@ -2972,17 +3988,19 @@ file so that decoders can recover the original data if desired. /* Set the true bit depth of the image data */ if (color_type & PNG_COLOR_MASK_COLOR) { - sig_bit.red = true_bit_depth; - sig_bit.green = true_bit_depth; - sig_bit.blue = true_bit_depth; + sig_bit.red = true_bit_depth; + sig_bit.green = true_bit_depth; + sig_bit.blue = true_bit_depth; } + else { - sig_bit.gray = true_bit_depth; + sig_bit.gray = true_bit_depth; } + if (color_type & PNG_COLOR_MASK_ALPHA) { - sig_bit.alpha = true_bit_depth; + sig_bit.alpha = true_bit_depth; } png_set_sBIT(png_ptr, info_ptr, &sig_bit); @@ -2994,7 +4012,7 @@ is required by PNG. png_set_shift(png_ptr, &sig_bit); -PNG files store 16 bit pixels in network byte order (big-endian, +PNG files store 16-bit pixels in network byte order (big-endian, ie. most significant bits first). This code would be used if they are supplied the other way (little-endian, i.e. least significant bits first, the way PCs store them): @@ -3028,11 +4046,24 @@ with You must supply the function - void write_transform_fn(png_ptr ptr, row_info_ptr + void write_transform_fn(png_structp png_ptr, png_row_infop row_info, png_bytep data) See pngtest.c for a working example. Your function will be called -before any of the other transformations are processed. +before any of the other transformations are processed. If supported +libpng also supplies an information routine that may be called from +your callback: + + png_get_current_row_number(png_ptr); + png_get_current_pass_number(png_ptr); + +This returns the current row passed to the transform. With interlaced +images the value returned is the row in the input sub-image image. Use +PNG_ROW_FROM_PASS_ROW(row, pass) and PNG_COL_FROM_PASS_COL(col, pass) to +find the output pixel (x,y) given an interlaced sub-image pixel (row,col,pass). + +The discussion of interlace handling above contains more information on how to +use these values. You can also set up a pointer to a user structure for use by your callback function. @@ -3114,25 +4145,39 @@ for details of which pixels to write when. If you don't want libpng to handle the interlacing details, just use png_set_interlace_handling() and call png_write_rows() the -correct number of times to write all seven sub-images. +correct number of times to write all the sub-images +(png_set_interlace_handling() returns the number of sub-images.) If you want libpng to build the sub-images, call this before you start writing any rows: - number_of_passes = - png_set_interlace_handling(png_ptr); + number_of_passes = png_set_interlace_handling(png_ptr); This will return the number of passes needed. Currently, this is seven, but may change if another interlace type is added. Then write the complete image number_of_passes times. - png_write_rows(png_ptr, row_pointers, - number_of_rows); + png_write_rows(png_ptr, row_pointers, number_of_rows); -As some of these rows are not used, and thus return immediately, you may -want to read about interlacing in the PNG specification, and only update -the rows that are actually used. +Think carefully before you write an interlaced image. Typically code that +reads such images reads all the image data into memory, uncompressed, before +doing any processing. Only code that can display an image on the fly can +take advantage of the interlacing and even then the image has to be exactly +the correct size for the output device, because scaling an image requires +adjacent pixels and these are not available until all the passes have been +read. + +If you do write an interlaced image you will hardly ever need to handle +the interlacing yourself. Call png_set_interlace_handling() and use the +approach described above. + +The only time it is conceivable that you will really need to write an +interlaced image pass-by-pass is when you have read one pass by pass and +made some pixel-by-pixel transformation to it, as described in the read +code above. In this case use the PNG_PASS_ROWS and PNG_PASS_COLS macros +to determine the size of each sub-image in turn and simply write the rows +you obtained from the read code. .SS Finishing a sequential write @@ -3151,6 +4196,7 @@ It is also possible to individually free the info_ptr members that point to libpng-allocated storage with the following function: png_free_data(png_ptr, info_ptr, mask, seq) + mask - identifies data to be freed, a mask containing the bitwise OR of one or more of @@ -3160,6 +4206,7 @@ point to libpng-allocated storage with the following function: PNG_FREE_SCAL, PNG_FREE_SPLT, PNG_FREE_TEXT, PNG_FREE_UNKN, or simply PNG_FREE_ALL + seq - sequence number of item to be freed (-1 for all items) @@ -3181,19 +4228,22 @@ or so that it will free data that was allocated by the user with png_malloc() or png_zalloc() and passed in via a png_set_*() function, with png_data_freer(png_ptr, info_ptr, freer, mask) - mask - which data elements are affected - same choices as in png_free_data() + freer - one of PNG_DESTROY_WILL_FREE_DATA PNG_SET_WILL_FREE_DATA PNG_USER_WILL_FREE_DATA + mask - which data elements are affected + same choices as in png_free_data() + For example, to transfer responsibility for some data from a read structure to a write structure, you could use png_data_freer(read_ptr, read_info_ptr, PNG_USER_WILL_FREE_DATA, PNG_FREE_PLTE|PNG_FREE_tRNS|PNG_FREE_hIST) + png_data_freer(write_ptr, write_info_ptr, PNG_DESTROY_WILL_FREE_DATA, PNG_FREE_PLTE|PNG_FREE_tRNS|PNG_FREE_hIST) @@ -3240,9 +4290,11 @@ these functions, call the appropriate png_set_*_fn() function. Memory allocation is done through the functions png_malloc(), png_calloc(), and png_free(). These currently just call the standard C functions. -png_calloc() calls png_malloc() and then png_memset() to clear the newly -allocated memory to zero. If your pointers can't access more then 64K -at a time, you will want to set MAXSEG_64K in zlib.h. Since it is +png_calloc() calls png_malloc() and then clears the newly +allocated memory to zero. There is limited support for certain systems +with segmented memory architectures and the types of pointers declared by +png.h match this; you will have to use appropriate pointers in your +application. Since it is unlikely that the method of handling memory allocation on a platform will change between applications, these functions must be modified in the library at compile time. If you prefer to use a different method @@ -3256,7 +4308,8 @@ via Your replacement memory functions must have prototypes as follows: png_voidp malloc_fn(png_structp png_ptr, - png_size_t size); + png_alloc_size_t size); + void free_fn(png_structp png_ptr, png_voidp ptr); Your malloc_fn() must return NULL in case of failure. The png_malloc() @@ -3289,8 +4342,10 @@ The replacement I/O functions must have prototypes as follows: void user_read_data(png_structp png_ptr, png_bytep data, png_size_t length); + void user_write_data(png_structp png_ptr, png_bytep data, png_size_t length); + void user_flush_data(png_structp png_ptr); The user_read_data() function is responsible for detecting and @@ -3307,8 +4362,9 @@ Error handling in libpng is done through png_error() and png_warning(). Errors handled through png_error() are fatal, meaning that png_error() should never return to its caller. Currently, this is handled via setjmp() and longjmp() (unless you have compiled libpng with -PNG_SETJMP_NOT_SUPPORTED, in which case it is handled via PNG_ABORT()), -but you could change this to do things like exit() if you should wish. +PNG_NO_SETJMP, in which case it is handled via PNG_ABORT()), +but you could change this to do things like exit() if you should wish, +as long as your function does not return. On non-fatal errors, png_warning() is called to print a warning message, and then control returns to the calling code. @@ -3334,6 +4390,7 @@ parameters as follows: void user_error_fn(png_structp png_ptr, png_const_charp error_msg); + void user_warning_fn(png_structp png_ptr, png_const_charp warning_msg); @@ -3371,7 +4428,7 @@ the simpler ones to get an idea of how they work. Try to find a similar transformation to the one you want to add and copy off of it. More details can be found in the comments inside the code itself. -.SS Configuring for 16 bit platforms +.SS Configuring for 16-bit platforms You will want to look into zconf.h to tell zlib (and thus libpng) that it cannot allocate more then 64K at a time. Even if you can, the memory @@ -3426,6 +4483,7 @@ specify no compression (Z_NO_COMPRESSION = 0), but this would create files larger than just storing the raw bitmap. You can specify the compression level by calling: + #include zlib.h png_set_compression_level(png_ptr, level); Another useful one is to reduce the memory level used by the library. @@ -3436,16 +4494,20 @@ other things, lower levels will result in sections of incompressible data being emitted in smaller stored blocks, with a correspondingly larger relative overhead of up to 15% in the worst case. + #include zlib.h png_set_compression_mem_level(png_ptr, level); The other functions are for configuring zlib. They are not recommended for normal use and may result in writing an invalid PNG file. See zlib.h for more information on what these mean. + #include zlib.h png_set_compression_strategy(png_ptr, strategy); + png_set_compression_window_bits(png_ptr, window_bits); + png_set_compression_method(png_ptr, method); png_set_compression_buffer_size(png_ptr, size); @@ -3535,6 +4597,8 @@ before recompiling libpng and save yourself code and data space, or you can turn off individual capabilities with defines that begin with PNG_NO_. +In libpng-1.5.0 and later, the #define's are in pnglibconf.h instead. + You can also turn all of the transforms and ancillary chunk capabilities off en masse with compiler directives that define PNG_NO_READ[or WRITE]_TRANSFORMS, or PNG_NO_READ[or WRITE]_ANCILLARY_CHUNKS, @@ -3587,8 +4651,8 @@ according to printf-style formatting directives. For example, is expanded to - if(PNG_DEBUG > 2) - fprintf(PNG_DEBUG_FILE, "foo=%d\n", foo); + if (PNG_DEBUG > 2) + fprintf(PNG_DEBUG_FILE, "foo=%d\n", foo); When PNG_DEBUG is defined but is zero, the macros aren't defined, but you can still use PNG_DEBUG to control your own debugging: @@ -3609,11 +4673,13 @@ Libpng can support some of these extensions. To enable them, use the png_permit_mng_features() function: feature_set = png_permit_mng_features(png_ptr, mask) + mask is a png_uint_32 containing the bitwise OR of the features you want to enable. These include PNG_FLAG_MNG_EMPTY_PLTE PNG_FLAG_MNG_FILTER_64 PNG_ALL_MNG_FEATURES + feature_set is a png_uint_32 that is the bitwise AND of your mask with the set of MNG features that is supported by the version of libpng that you are using. @@ -3638,7 +4704,7 @@ still alive and well, but they have moved on to other things. The old libpng functions png_read_init(), png_write_init(), png_info_init(), png_read_destroy(), and png_write_destroy() have been moved to PNG_INTERNAL in version 0.95 to discourage their use. These -functions will be removed from libpng version 2.0.0. +functions will be removed from libpng version 1.4.0. The preferred method of creating and initializing the libpng structures is via the png_create_read_struct(), png_create_write_struct(), and @@ -3827,21 +4893,29 @@ png_get_mmx_bitdepth_threshold(), png_get_mmx_rowbytes_threshold(), png_set_asm_flags(), and png_mmx_supported() We removed the obsolete png_check_sig(), png_memcpy_check(), and -png_memset_check() functions. Instead use !png_sig_cmp(), png_memcpy(), -and png_memset(), respectively. +png_memset_check() functions. Instead use !png_sig_cmp(), memcpy(), +and memset(), respectively. The function png_set_gray_1_2_4_to_8() was removed. It has been deprecated since libpng-1.0.18 and 1.2.9, when it was replaced with png_set_expand_gray_1_2_4_to_8() because the former function also -expanded palette images. +expanded any tRNS chunk to an alpha channel. + +Macros for png_get_uint_16, png_get_uint_32, and png_get_int_32 +were added and are used by default instead of the corresponding +functions. Unfortunately, +from libpng-1.4.0 until 1.4.4, the png_get_uint_16 macro (but not the +function) incorrectly returned a value of type png_uint_32. We changed the prototype for png_malloc() from png_malloc(png_structp png_ptr, png_uint_32 size) to png_malloc(png_structp png_ptr, png_alloc_size_t size) +This also applies to the prototype for the user replacement malloc_fn(). + The png_calloc() function was added and is used in place of -of "png_malloc(); png_memset();" except in the case in png_read_png() +of "png_malloc(); memset();" except in the case in png_read_png() where the array consists of pointers; in this case a "for" loop is used after the png_malloc() to set the pointers to NULL, to give robust. behavior in case the application runs out of memory part-way through @@ -3859,9 +4933,309 @@ The png_zalloc() and png_zfree() functions are no longer exported. The png_zalloc() function no longer zeroes out the memory that it allocates. +Support for dithering was disabled by default in libpng-1.4.0, because +it has not been well tested and doesn't actually "dither". +The code was not +removed, however, and could be enabled by building libpng with +PNG_READ_DITHER_SUPPORTED defined. In libpng-1.4.2, this support +was reenabled, but the function was renamed png_set_quantize() to +reflect more accurately what it actually does. At the same time, +the PNG_DITHER_[RED,GREEN_BLUE]_BITS macros were also renamed to +PNG_QUANTIZE_[RED,GREEN,BLUE]_BITS, and PNG_READ_DITHER_SUPPORTED +was renamed to PNG_READ_QUANTIZE_SUPPORTED. + We removed the trailing '.' from the warning and error messages. -.SH X. Detecting libpng +.SH X. Changes to Libpng from version 1.4.x to 1.5.x + +From libpng-1.4.0 until 1.4.4, the png_get_uint_16 macro (but not the +function) incorrectly returned a value of type png_uint_32. + +A. Changes that affect users of libpng + +There are no substantial API changes between the non-deprecated parts of +the 1.4.5 API and the 1.5.0 API, however the ability to directly access +the main libpng control structures, png_struct and png_info, deprecated +in earlier versions of libpng, has been completely removed from +libpng 1.5. + +We no longer include zlib.h in png.h. Applications that need access +to information in zlib.h will need to add the '#include "zlib.h"' +directive. It does not matter whether it is placed prior to or after +the '"#include png.h"' directive. + +We moved the png_strcpy(), png_strncpy(), png_strlen(), png_memcpy(), +png_memcmp(), png_sprintf, and png_memcpy() macros into a private +header file (pngpriv.h) that is not accessible to applications. + +In png_get_iCCP, the type of "profile" was changed from png_charpp +to png_bytepp, and in png_set_iCCP, from png_charp to png_const_bytep. + +There are changes of form in png.h, including new and changed macros to +declare +parts of the API. Some API functions with arguments that are pointers to +data not modified within the function have been corrected to declare +these arguments with PNG_CONST. + +Much of the internal use of C macros to control the library build has also +changed and some of this is visible in the exported header files, in +particular the use of macros to control data and API elements visible +during application compilation may require significant revision to +application code. (It is extremely rare for an application to do this.) + +Any program that compiled against libpng 1.4 and did not use deprecated +features or access internal library structures should compile and work +against libpng 1.5, except for the change in the prototype for +png_get_iCCP() and png_set_iCCP() API functions mentioned above. + +libpng 1.5.0 adds PNG_ PASS macros to help in the reading and writing of +interlaced images. The macros return the number of rows and columns in +each pass and information that can be used to de-interlace and (if +absolutely necessary) interlace an image. + +libpng 1.5.0 adds an API png_longjmp(png_ptr, value). This API calls +the application-provided png_longjmp_ptr on the internal, but application +initialized, jmpbuf. It is provided as a convenience to avoid the need +initialized, longjmp buffer. It is provided as a convenience to avoid +the need to use the png_jmpbuf macro, which had the unnecessary side +effect of resetting the internal png_longjmp_ptr value. + +libpng 1.5.0 includes a complete fixed point API. By default this is +present along with the corresponding floating point API. In general the +fixed point API is faster and smaller than the floating point one because +the PNG file format used fixed point, not floating point. This applies +even if the library uses floating point in internal calculations. A new +macro, PNG_FLOATING_ARITHMETIC_SUPPORTED, reveals whether the library +uses floating point arithmetic (the default) or fixed point arithmetic +internally for performance critical calculations such as gamma correction. +In some cases, the gamma calculations may produce slightly different +results. This has changed the results in png_rgb_to_gray and in alpha +composition (png_set_background for example). This applies even if the +original image was already linear (gamma == 1.0) and, therefore, it is +not necessary to linearize the image. This is because libpng has *not* +been changed to optimize that case correctly, yet. + +Fixed point support for the sCAL chunk comes with an important caveat; +the sCAL specification uses a decimal encoding of floating point values +and the accuracy of PNG fixed point values is insufficient for +representation of these values. Consequently a "string" API +(png_get_sCAL_s and png_set_sCAL_s) is the only reliable way of reading +arbitrary sCAL chunks in the absence of either the floating point API or +internal floating point calculations. + +Applications no longer need to include the optional distribution header +file pngusr.h or define the corresponding macros during application +build in order to see the correct variant of the libpng API. From 1.5.0 +application code can check for the corresponding _SUPPORTED macro: + +#ifdef PNG_INCH_CONVERSIONS_SUPPORTED + /* code that uses the inch conversion APIs. */ +#endif + +This macro will only be defined if the inch conversion functions have been +compiled into libpng. The full set of macros, and whether or not support +has been compiled in, are available in the header file pnglibconf.h. +This header file is specific to the libpng build. Notice that prior to +1.5.0 the _SUPPORTED macros would always have the default definition unless +reset by pngusr.h or by explicit settings on the compiler command line. +These settings may produce compiler warnings or errors in 1.5.0 because +of macro redefinition. + +From libpng-1.4.0 until 1.4.4, the png_get_uint_16 macro (but not the +function) incorrectly returned a value of type png_uint_32. libpng 1.5.0 +is consistent with the implementation in 1.4.5 and 1.2.x (where the macro +did not exist.) + +Applications can now choose whether to use these macros or to call the +corresponding function by defining PNG_USE_READ_MACROS or +PNG_NO_USE_READ_MACROS before including png.h. Notice that this is +only supported from 1.5.0 -defining PNG_NO_USE_READ_MACROS prior to 1.5.0 + will lead to a link failure. + +Prior to libpng-1.5.4, the zlib compressor used the same set of parameters +when compressing the IDAT data and textual data such as zTXt and iCCP. +In libpng-1.5.4 we reinitialized the zlib stream for each type of data. +We added five png_set_text_*() functions for setting the parameters to +use with textual data. + +Prior to libpng-1.5.4, the PNG_READ_16_TO_8_ACCURATE_SCALE_SUPPORTED +option was off by default, and slightly inaccurate scaling occurred. +This option can no longer be turned off, and the choice of accurate +or inaccurate 16-to-8 scaling is by using the new png_set_scale_16_to_8() +API for accurate scaling or the old png_set_strip_16_to_8() API for simple +chopping. + +Prior to libpng-1.5.4, the png_set_user_limits() function could only be +used to reduce the width and height limits from the value of +PNG_USER_WIDTH_MAX and PNG_USER_HEIGHT_MAX, although this document said +that it could be used to override them. Now this function will reduce or +increase the limits. + +B. Changes to the build and configuration of libpng + +Details of internal changes to the library code can be found in the CHANGES +file. These will be of no concern to the vast majority of library users or +builders, however the few who configure libpng to a non-default feature +set may need to change how this is done. + +There should be no need for library builders to alter build scripts if +these use the distributed build support - configure or the makefiles - +however users of the makefiles may care to update their build scripts +to build pnglibconf.h where the corresponding makefile does not do so. + +Building libpng with a non-default configuration has changed completely. +The old method using pngusr.h should still work correctly even though the +way pngusr.h is used in the build has been changed, however library +builders will probably want to examine the changes to take advantage of +new capabilities and to simplify their build system. + +B.1 Specific changes to library configuration capabilities + +The library now supports a complete fixed point implementation and can +thus be used on systems which have no floating point support or very +limited or slow support. Previously gamma correction, an essential part +of complete PNG support, required reasonably fast floating point. + +As part of this the choice of internal implementation has been made +independent of the choice of fixed versus floating point APIs and all the +missing fixed point APIs have been implemented. + +The exact mechanism used to control attributes of API functions has +changed. A single set of operating system independent macro definitions +is used and operating system specific directives are defined in +pnglibconf.h + +As part of this the mechanism used to choose procedure call standards on +those systems that allow a choice has been changed. At present this only +affects certain Microsoft (DOS, Windows) and IBM (OS/2) operating systems +running on Intel processors. As before PNGAPI is defined where required +to control the exported API functions; however, two new macros, PNGCBAPI +and PNGCAPI, are used instead for callback functions (PNGCBAPI) and +(PNGCAPI) for functions that must match a C library prototype (currently +only png_longjmp_ptr, which must match the C longjmp function.) The new +approach is documented in pngconf.h + +Despite these changes libpng 1.5.0 only supports the native C function +calling standard on those platforms tested so far (__cdecl on Microsoft +Windows). This is because the support requirements for alternative +calling conventions seem to no longer exist. Developers who find it +necessary to set PNG_API_RULE to 1 should advise the mailing list +(png-mng-implement) of this and library builders who use Openwatcom and +therefore set PNG_API_RULE to 2 should also contact the mailing list. + +A new test program, pngvalid, is provided in addition to pngtest. +pngvalid validates the arithmetic accuracy of the gamma correction +calculations and includes a number of validations of the file format. +A subset of the full range of tests is run when "make check" is done +(in the 'configure' build.) pngvalid also allows total allocated memory +usage to be evaluated and performs additional memory overwrite validation. + +Many changes to individual feature macros have been made. The following +are the changes most likely to be noticed by library builders who +configure libpng: + +1) All feature macros now have consistent naming: + +#define PNG_NO_feature turns the feature off +#define PNG_feature_SUPPORTED turns the feature on + +pnglibconf.h contains one line for each feature macro which is either: + +#define PNG_feature_SUPPORTED + +if the feature is supported or: + +/*#undef PNG_feature_SUPPORTED*/ + +if it is not. Library code consistently checks for the 'SUPPORTED' macro. +It does not, and should not, check for the 'NO' macro which will not +normally be defined even if the feature is not supported. + +Compatibility with the old names is provided as follows: + +PNG_INCH_CONVERSIONS turns on PNG_INCH_CONVERSIONS_SUPPORTED + +And the following definitions disable the corresponding feature: + +PNG_SETJMP_NOT_SUPPORTED disables SETJMP +PNG_READ_TRANSFORMS_NOT_SUPPORTED disables READ_TRANSFORMS +PNG_NO_READ_COMPOSITED_NODIV disables READ_COMPOSITE_NODIV +PNG_WRITE_TRANSFORMS_NOT_SUPPORTED disables WRITE_TRANSFORMS +PNG_READ_ANCILLARY_CHUNKS_NOT_SUPPORTED disables READ_ANCILLARY_CHUNKS +PNG_WRITE_ANCILLARY_CHUNKS_NOT_SUPPORTED disables WRITE_ANCILLARY_CHUNKS + +Library builders should remove use of the above, inconsistent, names. + +2) Warning and error message formatting was previously conditional on +the STDIO feature. The library has been changed to use the +CONSOLE_IO feature instead. This means that if CONSOLE_IO is disabled +the library no longer uses the printf(3) functions, even though the +default read/write implementations use (FILE) style stdio.h functions. + +3) Three feature macros now control the fixed/floating point decisions: + +PNG_FLOATING_POINT_SUPPORTED enables the floating point APIs + +PNG_FIXED_POINT_SUPPORTED enables the fixed point APIs; however, in +practice these are normally required internally anyway (because the PNG +file format is fixed point), therefore in most cases PNG_NO_FIXED_POINT +merely stops the function from being exported. + +PNG_FLOATING_ARITHMETIC_SUPPORTED chooses between the internal floating +point implementation or the fixed point one. Typically the fixed point +implementation is larger and slower than the floating point implementation +on a system that supports floating point, however it may be faster on a +system which lacks floating point hardware and therefore uses a software +emulation. + +4) Added PNG_{READ,WRITE}_INT_FUNCTIONS_SUPPORTED. This allows the +functions to read and write ints to be disabled independently of +PNG_USE_READ_MACROS, which allows libpng to be built with the functions +even though the default is to use the macros - this allows applications +to choose at app buildtime whether or not to use macros (previously +impossible because the functions weren't in the default build.) + +B.2 Changes to the configuration mechanism + +Prior to libpng-1.5.0 library builders who needed to configure libpng +had either to modify the exported pngconf.h header file to add system +specific configuration or had to write feature selection macros into +pngusr.h and cause this to be included into pngconf.h by defining +PNG_USER_CONFIG. The latter mechanism had the disadvantage that an +application built without PNG_USER_CONFIG defined would see the +unmodified, default, libpng API and thus would probably fail to link. + +These mechanisms still work in the configure build and in any makefile +build that builds pnglibconf.h although the feature selection macros +have changed somewhat as described above. In 1.5.0, however, pngusr.h is +processed only once, when the exported header file pnglibconf.h is built. +pngconf.h no longer includes pngusr.h, therefore it is ignored after the +build of pnglibconf.h and it is never included in an application build. + +The rarely used alternative of adding a list of feature macros to the +CFLAGS setting in the build also still works, however the macros will be +copied to pnglibconf.h and this may produce macro redefinition warnings +when the individual C files are compiled. + +All configuration now only works if pnglibconf.h is built from +scripts/pnglibconf.dfa. This requires the program awk. Brian Kernighan +(the original author of awk) maintains C source code of that awk and this +and all known later implementations (often called by subtly different +names - nawk and gawk for example) are adequate to build pnglibconf.h. +The Sun Microsystems (now Oracle) program 'awk' is an earlier version +and does not work, this may also apply to other systems that have a +functioning awk called 'nawk'. + +Configuration options are now documented in scripts/pnglibconf.dfa. This +file also includes dependency information that ensures a configuration is +consistent; that is, if a feature is switched off dependent features are +also removed. As a recommended alternative to using feature macros in +pngusr.h a system builder may also define equivalent options in pngusr.dfa +(or, indeed, any file) and add that to the configuration by setting +DFA_XTRA to the file name. The makefiles in contrib/pngminim illustrate +how to do this, and a case where pngusr.h is still required. + +.SH XI. Detecting libpng The png_get_io_ptr() function has been present since libpng-0.88, has never changed, and is unaffected by conditional compilation macros. It is the @@ -3870,7 +5244,7 @@ libpng version since 0.88. In an autoconf "configure.in" you could use AC_CHECK_LIB(png, png_get_io_ptr, ... -.SH XI. Source code repository +.SH XII. Source code repository Since about February 2009, version 1.2.34, libpng has been under "git" source control. The git repository was built from old libpng-x.y.z.tar.gz files @@ -3889,7 +5263,12 @@ the libpng bug tracker at http://libpng.sourceforge.net -.SH XII. Coding style +We also accept patches built from the tar or zip distributions, and +simple verbal discriptions of bug fixes, reported either to the +SourceForge bug tracker or to the png-mng-implement at lists.sf.net +mailing list. + +.SH XIII. Coding style Our coding style is similar to the "Allman" style, with curly braces on separate lines: @@ -3928,12 +5307,12 @@ the statement that follows the comment: /* Single-line comment */ statement; - /* Multiple-line - * comment + /* This is a multiple-line + * comment. */ statement; -Very short comments can be placed at the end of the statement +Very short comments can be placed after the end of the statement to which they pertain: statement; /* comment */ @@ -3946,7 +5325,7 @@ Functions and their curly braces are not indented, and exported functions are marked with PNGAPI: /* This is a public function that is visible to - * application programers. It does thus-and-so. + * application programmers. It does thus-and-so. */ void PNGAPI png_exported_function(png_ptr, png_info, foo) @@ -3974,15 +5353,16 @@ above the comment that says /* Maintainer: Put new private prototypes here ^ and in libpngpf.3 */ -The names of all exported functions and variables begin -with "png_", and all publicly visible C preprocessor -macros begin with "PNG_". +To avoid polluting the global namespace, the names of all exported +functions and variables begin with "png_", and all publicly visible C +preprocessor macros begin with "PNG_". We request that applications that +use libpng *not* begin any of their own symbols with either of these strings. We put a space after each comma and after each semicolon -in "for" statments, and we put spaces before and after each -C binary operator and after "for" or "while". We don't -put a space between a typecast and the expression being -cast, nor do we put one between a function name and the +in "for" statements, and we put spaces before and after each +C binary operator and after "for" or "while", and before +"?". We don't put a space between a typecast and the expression +being cast, nor do we put one between a function name and the left parenthesis that follows it: for (i = 2; i > 0; --i) @@ -3997,15 +5377,15 @@ Lines do not exceed 80 characters. Other rules can be inferred by inspecting the libpng source. -.SH XIII. Y2K Compliance in libpng +.SH XIV. Y2K Compliance in libpng -January 3, 2010 +July 7, 2011 Since the PNG Development group is an ad-hoc body, we can't make an official declaration. This is your unofficial assurance that libpng from version 0.71 and -upward through 1.4.0 are Y2K compliant. It is my belief that earlier +upward through 1.5.4 are Y2K compliant. It is my belief that earlier versions were also Y2K compliant. Libpng only has three year fields. One is a 2-byte unsigned integer that @@ -4178,6 +5558,29 @@ the first widely used release: 1.4.0beta88-109 14 10400 14.so.14.0[.0] 1.4.0rc02-08 14 10400 14.so.14.0[.0] 1.4.0 14 10400 14.so.14.0[.0] + 1.4.1beta01-03 14 10401 14.so.14.1[.0] + 1.4.1rc01 14 10401 14.so.14.1[.0] + 1.4.1beta04-12 14 10401 14.so.14.1[.0] + 1.4.1 14 10401 14.so.14.1[.0] + 1.4.2 14 10402 14.so.14.2[.0] + 1.4.3 14 10403 14.so.14.3[.0] + 1.4.4 14 10404 14.so.14.4[.0] + 1.5.0beta01-58 15 10500 15.so.15.0[.0] + 1.5.0rc01-07 15 10500 15.so.15.0[.0] + 1.5.0 15 10500 15.so.15.0[.0] + 1.5.1beta01-11 15 10501 15.so.15.1[.0] + 1.5.1rc01-02 15 10501 15.so.15.1[.0] + 1.5.1 15 10501 15.so.15.1[.0] + 1.5.2beta01-03 15 10502 15.so.15.2[.0] + 1.5.2rc01-03 15 10502 15.so.15.2[.0] + 1.5.2 15 10502 15.so.15.2[.0] + 1.5.3beta01-10 15 10503 15.so.15.3[.0] + 1.5.3rc01-02 15 10503 15.so.15.3[.0] + 1.5.3beta11 15 10503 15.so.15.3[.0] + 1.5.3 [omitted] + 1.5.4beta01-08 15 10504 15.so.15.4[.0] + 1.5.4rc01 15 10504 15.so.15.4[.0] + 1.5.4 15 10504 15.so.15.4[.0] Henceforth the source version will match the shared-library minor and patch numbers; the shared-library major version number will be @@ -4190,7 +5593,8 @@ version 1.0.6j; from then on they were given the upcoming public release number plus "betaNN" or "rcN". .SH "SEE ALSO" -libpngpf(3), png(5) +.BR "png"(5), " libpngpf"(3), " zlib"(3), " deflate"(5), " " and " zlib"(5) + .LP .IR libpng : .IP @@ -4233,7 +5637,7 @@ possible without all of you. Thanks to Frank J. T. Wojcik for helping with the documentation. -Libpng version 1.4.0 - January 3, 2010: +Libpng version 1.5.4 - July 7, 2011: Initially created in 1995 by Guy Eric Schalnat, then of Group 42, Inc. Currently maintained by Glenn Randers-Pehrson (glennrp at users.sourceforge.net). @@ -4256,7 +5660,7 @@ this sentence. This code is released under the libpng license. -libpng versions 1.2.6, August 15, 2004, through 1.4.0, January 3, 2010, are +libpng versions 1.2.6, August 15, 2004, through 1.5.4, July 7, 2011, are Copyright (c) 2004,2006-2007 Glenn Randers-Pehrson, and are distributed according to the same disclaimer and license as libpng-1.2.5 with the following individual added to the list of Contributing Authors @@ -4355,7 +5759,7 @@ certification mark of the Open Source Initiative. Glenn Randers-Pehrson glennrp at users.sourceforge.net -January 3, 2010 +July 7, 2011 .\" end of man page |