diff options
Diffstat (limited to 'src/lodepng.cpp')
| -rw-r--r-- | src/lodepng.cpp | 67 |
1 files changed, 65 insertions, 2 deletions
diff --git a/src/lodepng.cpp b/src/lodepng.cpp index 8da4293..638dbf4 100644 --- a/src/lodepng.cpp +++ b/src/lodepng.cpp @@ -31,6 +31,8 @@ You are free to name this file lodepng.cpp or lodepng.c depending on your usage. #include "lodepng.h" #include "portable.h" +#define USE_BRUTE_FORCE_ENCODING 1 + #define VERSION_STRING "20080927" /* ////////////////////////////////////////////////////////////////////////// */ @@ -1033,14 +1035,71 @@ static void addLengthDistance(uivector* values, size_t length, size_t distance) uivector_push_back(values, extra_distance); } -#if 0 +#if USE_BRUTE_FORCE_ENCODING +#define encodeLZ77 encodeLZ77_brute /*the "brute force" version of the encodeLZ7 algorithm, not used anymore, kept here for reference*/ -static void encodeLZ77_brute(uivector* out, const unsigned char* in, size_t size, unsigned windowSize) +static unsigned encodeLZ77_brute(uivector* out, const unsigned char* in, size_t size, unsigned windowSize) { size_t pos; /*using pointer instead of vector for input makes it faster when NOT using optimization when compiling; no influence if optimization is used*/ for(pos = 0; pos < size; pos++) { + /*Phase 1: doxygen images often have long runs of the same color, try to find them*/ + const int minLength = 4; // Minimum length for a run to make sense + + if(pos < size - minLength * 4) + { + size_t p, fp; + size_t current_length; + + /*RGBA pixel run?*/ + p = pos; + fp = pos + 4; + current_length = 0; + + while(fp < size && in[p] == in[fp] && current_length < MAX_SUPPORTED_DEFLATE_LENGTH) + { + ++p; + ++fp; + ++current_length; + } + + if (current_length > (minLength - 1 ) * 4) /*worth using?*/ + { + uivector_push_back(out, in[pos ]); + uivector_push_back(out, in[pos + 1]); + uivector_push_back(out, in[pos + 2]); + uivector_push_back(out, in[pos + 3]); + addLengthDistance(out, current_length, 4); + + pos += current_length + 4 - 1; /*-1 for loop's pos++*/ + continue; + } + + /*RGB pixel run?*/ + p = pos; + fp = pos + 3; + current_length = 0; + + while(fp < size && in[p] == in[fp] && current_length < MAX_SUPPORTED_DEFLATE_LENGTH) + { + ++p; + ++fp; + ++current_length; + } + + if (current_length > (minLength - 1 ) * 3) /*worth using?*/ + { + uivector_push_back(out, in[pos ]); + uivector_push_back(out, in[pos + 1]); + uivector_push_back(out, in[pos + 2]); + addLengthDistance(out, current_length, 3); + + pos += current_length + 3 - 1; /*-1 for loop's pos++*/ + continue; + } + } + size_t length = 0, offset = 0; /*the length and offset found for the current position*/ size_t max_offset = pos < windowSize ? pos : windowSize; /*how far back to test*/ size_t current_offset; @@ -1082,6 +1141,8 @@ static void encodeLZ77_brute(uivector* out, const unsigned char* in, size_t size pos += (length - 1); } } /*end of the loop through each character of input*/ + + return 0; } #endif @@ -1094,6 +1155,7 @@ making HASH_NUM_CHARACTERS larger (like 8), makes the file size larger but is a making HASH_NUM_CHARACTERS smaller (like 3), makes the file size smaller but is slower */ +#if !defined(USE_BRUTE_FORCE_ENCODING) static unsigned getHash(const unsigned char* data, size_t size, size_t pos) { unsigned result = 0; @@ -1195,6 +1257,7 @@ static unsigned encodeLZ77(uivector* out, const unsigned char* in, size_t size, uivector_cleanup(&tablepos2); return error; } +#endif /* /////////////////////////////////////////////////////////////////////////// */ |