diff options
Diffstat (limited to 'src')
| -rw-r--r-- | src/Fl_GIF_Image.cxx | 52 |
1 files changed, 42 insertions, 10 deletions
diff --git a/src/Fl_GIF_Image.cxx b/src/Fl_GIF_Image.cxx index 682d251df..97adb23ce 100644 --- a/src/Fl_GIF_Image.cxx +++ b/src/Fl_GIF_Image.cxx @@ -3,7 +3,7 @@ // // Fl_GIF_Image routines. // -// Copyright 1997-2015 by Bill Spitzak and others. +// Copyright 1997-2019 by Bill Spitzak and others. // // This library is free software. Distribution and use rights are outlined in // the file "COPYING" which should have been included with this file. If this @@ -20,6 +20,16 @@ // // +// Reference: GIF89a Specification (links valid as of Jan 05, 2019): +// +// "GRAPHICS INTERCHANGE FORMAT(sm), Version 89a" (authoritative): +// https://www.w3.org/Graphics/GIF/spec-gif89a.txt +// +// HTML version (non-authoritative): +// https://web.archive.org/web/20160304075538/http://qalle.net/gif89a.php +// + +// // Include necessary header files... // @@ -113,7 +123,12 @@ Fl_GIF_Image::Fl_GIF_Image(const char *infname) : Fl_Pixmap((char *const*)0) { uchar ch = NEXTBYTE; char HasColormap = ((ch & 0x80) != 0); int BitsPerPixel = (ch & 7) + 1; - int ColorMapSize = 1 << BitsPerPixel; + int ColorMapSize; + if (HasColormap) { + ColorMapSize = 2 << (ch & 7); + } else { + ColorMapSize = 0; + } // int OriginalResolution = ((ch>>4)&7)+1; // int SortedTable = (ch&8)!=0; ch = NEXTBYTE; // Background Color index @@ -129,10 +144,6 @@ Fl_GIF_Image::Fl_GIF_Image(const char *infname) : Fl_Pixmap((char *const*)0) { Green[i] = NEXTBYTE; Blue[i] = NEXTBYTE; } - } else { - Fl::warning("%s does not have a colormap.", infname); - for (int i = 0; i < ColorMapSize; i++) - Red[i] = Green[i] = Blue[i] = (uchar)(255 * i / (ColorMapSize-1)); } int CodeSize; /* Code size, init from GIF header, increases... */ @@ -179,10 +190,10 @@ Fl_GIF_Image::Fl_GIF_Image(const char *infname) : Fl_Pixmap((char *const*)0) { GETSHORT(Height); ch = NEXTBYTE; Interlace = ((ch & 0x40) != 0); - if (ch&0x80) { - // read local color map - int n = 2<<(ch&7); - for (i=0; i < n; i++) { + if (ch & 0x80) { // image has local color table + BitsPerPixel = (ch & 7) + 1; + ColorMapSize = 2 << (ch & 7); + for (i=0; i < ColorMapSize; i++) { Red[i] = NEXTBYTE; Green[i] = NEXTBYTE; Blue[i] = NEXTBYTE; @@ -206,6 +217,27 @@ Fl_GIF_Image::Fl_GIF_Image(const char *infname) : Fl_Pixmap((char *const*)0) { ColorMapSize = 1 << BitsPerPixel; } + // Fix images w/o color table. The standard allows this and lets the + // decoder choose a default color table. The standard recommends the + // first two color table entries should be black and white. + + if (ColorMapSize == 0) { // no global and no local color table + Fl::warning("%s does not have a color table, using default.\n", infname); + BitsPerPixel = CodeSize - 1; + ColorMapSize = 1 << BitsPerPixel; + Red[0] = Green[0] = Blue[0] = 0; // black + Red[1] = Green[1] = Blue[1] = 255; // white + for (int i = 2; i < ColorMapSize; i++) { + Red[i] = Green[i] = Blue[i] = (uchar)(255 * i / (ColorMapSize - 1)); + } +#if (0) + // fill color table to maximum size + for (int i = ColorMapSize; i < 256; i++) { + Red[i] = Green[i] = Blue[i] = 0; // black + } +#endif + } + uchar *Image = new uchar[Width*Height]; int YC = 0, Pass = 0; /* Used to de-interlace the picture */ |