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Leave animated PNGs to the OptiPNG pass #159

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Leave animated PNGs to the OptiPNG pass #159

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13 changes: 13 additions & 0 deletions src/zopflipng.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -518,6 +518,16 @@ static unsigned ZopfliPNGOptimize(const char * Infile, const std::vector<unsigne
return 0;
}

static bool IsAPNG(const std::vector<unsigned char>& png) {
if (png.size() < 8) {return false;}
const unsigned char* end = png.data() + png.size();
for (const unsigned char* chunk = png.data() + 8; end - chunk >= 12; chunk = lodepng_chunk_next_const(chunk, end)) {
if (lodepng_chunk_type_equals(chunk, "acTL")) {return true;}
if (lodepng_chunk_type_equals(chunk, "IDAT")) {return false;}
}
return false;
}

int Zopflipng(bool strip, const char * Infile, bool strict, unsigned Mode, int filter, unsigned multithreading, unsigned quiet) {
ZopfliPNGOptions png_options;
png_options.Mode = Mode;
Expand All @@ -535,6 +545,9 @@ int Zopflipng(bool strip, const char * Infile, bool strict, unsigned Mode, int f
fprintf(stderr, "Could not load PNG %s\n", Infile);
return -1;
}
// APNG frames (fdAT) are copied unchanged and would no longer match a reduced
// color type, so leave APNGs alone here; the OptiPNG pass does not reduce them.
if (IsAPNG(origpng)) {return 1;}
if (filter == 6){
lodepng::getFilterTypes(filters, origpng);
if(!filters.size()){
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