diff options
| -rw-r--r-- | generic/tkImgGIF.c | 207 |
1 files changed, 44 insertions, 163 deletions
diff --git a/generic/tkImgGIF.c b/generic/tkImgGIF.c index 52ba2d7..87a90c7 100644 --- a/generic/tkImgGIF.c +++ b/generic/tkImgGIF.c @@ -29,7 +29,7 @@ * | provided "as is" without express or implied warranty. | * +-------------------------------------------------------------------+ * - * RCS: @(#) $Id: tkImgGIF.c,v 1.9 2000/01/26 21:11:00 ericm Exp $ + * RCS: @(#) $Id: tkImgGIF.c,v 1.10 2000/01/27 16:58:42 ericm Exp $ */ /* @@ -131,8 +131,6 @@ static int GetCode _ANSI_ARGS_((Tcl_Channel chan, int code_size, int flag)); static int GetDataBlock _ANSI_ARGS_((Tcl_Channel chan, unsigned char *buf)); -static int LWZReadByte _ANSI_ARGS_((Tcl_Channel chan, int flag, - int input_code_size)); static int ReadColorMap _ANSI_ARGS_((Tcl_Channel chan, int number, unsigned char buffer[MAXCOLORMAPSIZE][4])); static int ReadGIFHeader _ANSI_ARGS_((Tcl_Channel chan, @@ -229,6 +227,7 @@ FileReadGIF(interp, chan, fileName, format, imageHandle, destX, destY, Tcl_Obj **objv; Tk_PhotoImageBlock block; unsigned char buf[100]; + unsigned char *trashBuffer = NULL; int bitPixel; unsigned char colorMap[MAXCOLORMAPSIZE][4]; int transparent = -1; @@ -361,37 +360,49 @@ FileReadGIF(interp, chan, fileName, format, imageHandle, destX, destY, bitPixel = 1<<((buf[8]&0x07)+1); if (index--) { - int x,y; - unsigned char c; /* this is not the image we want to read: skip it. */ - if (BitSet(buf[8], LOCALCOLORMAP)) { - if (!ReadColorMap(chan, bitPixel, 0)) { + if (!ReadColorMap(chan, bitPixel, colorMap)) { Tcl_AppendResult(interp, "error reading color map", (char *) NULL); goto error; } } - /* read data */ - if (!ReadOK(chan,&c,1)) { - goto error; + /* If we've not yet allocated a trash buffer, do so now */ + if (trashBuffer == NULL) { + nBytes = fileWidth * fileHeight * 3; + trashBuffer = + (unsigned char *) ckalloc((unsigned int) nBytes); } - LWZReadByte(chan, 1, c); - - for (y=0; y<fileHeight; y++) { - for (x=0; x<fileWidth; x++) { - if (LWZReadByte(chan, 0, c) < 0) { - Tcl_AppendResult(interp, - "error reading image data", (char *) NULL); - goto error; - } - } + /* + * Slurp! Process the data for this image and stuff it in a + * trash buffer. + * + * Yes, it might be more efficient here to *not* store the data + * (we're just going to throw it away later). However, I elected + * to implement it this way for good reasons. First, I wanted to + * avoid duplicating the (fairly complex) LWZ decoder in ReadImage. + * Fine, you say, why didn't you just modify it to allow the use of + * a NULL specifier for the output buffer? I tried that, but it + * negatively impacted the performance of what I think will be the + * common case: reading the first image in the file. Rather than + * marginally improve the speed of the less frequent case, I chose + * to maintain high performance for the common case. + */ + if (ReadImage(interp, trashBuffer, chan, fileWidth, + fileHeight, colorMap, 0, 0, 0, 0, 0, -1) != TCL_OK) { + goto error; } continue; } + /* If a trash buffer has been allocated, free it now */ + if (trashBuffer != NULL) { + ckfree((char *)trashBuffer); + trashBuffer = NULL; + } if (BitSet(buf[8], LOCALCOLORMAP)) { if (!ReadColorMap(chan, bitPixel, colorMap)) { Tcl_AppendResult(interp, "error reading color map", @@ -730,18 +741,11 @@ GetDataBlock(chan, buf) * which is (c) 2000 ImageMagick Studio. * * Some thoughts on our implementation: - * We currently have implementations for two separate GIF decoders in - * this source. One is here, in ReadImage; the other is in LWZReadByte. - * This is an artifact of our original implementation. Ideally, we - * should remove all vestiges of LWZReadByte, which is slow and poorly - * documented. However, that would require some additional effort to - * collapse the calling layers of this system: Instead of - * FileReadGIF -> ReadImage, it would change to FileReadGIF. + * It sure would be nice if ReadImage didn't take 11 parameters! I think + * that if we were smarter, we could avoid doing that. * * Possible further optimizations: we could pull the GetCode function - * directly into ReadImage, which would improve our speed. The reason - * I have not yet done so is because GetCode is still used by LWZReadByte, - * and I don't want to duplicate the code. + * directly into ReadImage, which would improve our speed. * * Results: * Processes a GIF image and loads the pixel data into a memory array. @@ -768,19 +772,18 @@ ReadImage(interp, imagePtr, chan, len, rows, cmap, unsigned char initialCodeSize; int v; int xpos = 0, ypos = 0, pass = 0, i; - char *pixelPtr; + register char *pixelPtr; const static int interlaceStep[] = { 8, 8, 4, 2 }; const static int interlaceStart[] = { 0, 4, 2, 1 }; unsigned short prefix[(1 << MAX_LWZ_BITS)]; unsigned char append[(1 << MAX_LWZ_BITS)]; unsigned char stack[(1 << MAX_LWZ_BITS)*2]; - unsigned char *top; + register unsigned char *top; int codeSize, clearCode, inCode, endCode, oldCode, maxCode, code, firstCode; - /* - * Initialize the decompression routines + * Initialize the decoder */ if (! ReadOK(chan, &initialCodeSize, 1)) { Tcl_AppendResult(interp, "error reading GIF image: ", @@ -920,6 +923,12 @@ ReadImage(interp, imagePtr, chan, len, rows, cmap, if (v < 0) { return TCL_OK; } + + /* + * If pixelPtr is null, we're skipping this image (presumably + * there are more in the file and we will be called to read + * one of them later) + */ *pixelPtr++ = cmap[v][CM_RED]; *pixelPtr++ = cmap[v][CM_GREEN]; *pixelPtr++ = cmap[v][CM_BLUE]; @@ -927,6 +936,7 @@ ReadImage(interp, imagePtr, chan, len, rows, cmap, *pixelPtr++ = cmap[v][CM_ALPHA]; } xpos++; + } /* If interlacing, the next ypos is not just +1 */ @@ -947,135 +957,6 @@ ReadImage(interp, imagePtr, chan, len, rows, cmap, return TCL_OK; } -static int -LWZReadByte(chan, flag, input_code_size) - Tcl_Channel chan; - int flag; - int input_code_size; -{ - static int fresh = 0; - int code, incode; - static int code_size, set_code_size; - static int max_code, max_code_size; - static int firstcode, oldcode; - static int clear_code, end_code; - static int prefix[(1 << MAX_LWZ_BITS)]; - static int append[(1 << MAX_LWZ_BITS)]; - static int stack[(1<<(MAX_LWZ_BITS))*2], *sp; - register int i; - - if (flag) { - set_code_size = input_code_size; - code_size = set_code_size+1; - clear_code = 1 << set_code_size ; - end_code = clear_code + 1; - max_code_size = 2*clear_code; - max_code = clear_code+2; - - /* Init the lwz unpacker */ - GetCode(chan, 0, 1); - - fresh = 1; - - /* Initialize prefix and append tables */ - memset((void *)prefix, 0, (1 << MAX_LWZ_BITS) * sizeof(int)); - memset((void *)append, 0, (1 << MAX_LWZ_BITS) * sizeof(int)); - for (i = 0; i < clear_code; ++i) { - append[i] = i; - } - sp = stack; - - return 0; - } else if (fresh) { - /* - * find the first "real" code and return that. Because of - * how LWZ works, it will necessarily refer to a single char, - * so we need not bother with the stack - */ - fresh = 0; - do { - firstcode = GetCode(chan, code_size, 0); - } while (firstcode == clear_code); - oldcode = firstcode; - return firstcode; - } - - if (sp > stack) { - return *--sp; - } - - while ((code = GetCode(chan, code_size, 0)) >= 0) { - if (code == clear_code) { - memset((void *)prefix, 0, (1 << MAX_LWZ_BITS) * sizeof(int)); - memset((void *)append, 0, (1 << MAX_LWZ_BITS) * sizeof(int)); - for (i = 0; i < clear_code; ++i) { - append[i] = i; - } - - code_size = set_code_size+1; - max_code_size = 2*clear_code; - max_code = clear_code+2; - sp = stack; - firstcode = oldcode = GetCode(chan, code_size, 0); - return firstcode; - - } else if (code == end_code) { - int count; - unsigned char buf[260]; - - if (ZeroDataBlock) { - return -2; - } - - while ((count = GetDataBlock(chan, buf)) > 0) - /* Empty body */; - - if (count != 0) { - return -2; - } - } - - incode = code; - - if (code >= max_code) { - *sp++ = firstcode; - code = oldcode; - } - - while (code >= clear_code) { - *sp++ = append[code]; - if (code == prefix[code]) { - return -2; - - /* - * Used to be this instead, Steve Ball suggested - * the change to just return. - printf("circular table entry BIG ERROR\n"); - */ - } - code = prefix[code]; - } - - *sp++ = firstcode = append[code]; - - if ((code = max_code) <(1<<MAX_LWZ_BITS)) { - prefix[code] = oldcode; - append[code] = firstcode; - ++max_code; - if ((max_code>=max_code_size) && (max_code_size < (1<<MAX_LWZ_BITS))) { - max_code_size *= 2; - ++code_size; - } - } - - oldcode = incode; - - if (sp > stack) - return *--sp; - } - return code; -} - /* *---------------------------------------------------------------------- |