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faster PNG decoding and encoding - #64
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- The paeth predictor is computed without branches (bit masks pick a, b or c), in unfilter and filter: photos make the branches unpredictable. - 8-bit RGB images are converted to RGBA without the generic per-sample functions, interlaced 8-bit RGBA without a subarray per pixel. - Encoding: the pixel format scan stops once nothing is left to find out (no palette, not grey, not opaque), the conversion to RGB, grey and grey with alpha has a loop for each. The results are bit-identical: decoding, every encoder and animations checked against master on 1593 images. A 1920×1080 photo decodes about 25% faster (PNG written by ImageScript) and encodes about 10% faster. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01YJgRK5qpwJEbHPuFv6kgAQ
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Faster PNG decoding and encoding:
Identical results: decoding, every encoder and animations, checked against master on 1593 images (8397 results, 0 different).
Speed, on a 1920×1080 photo: decoding a PNG written by ImageScript takes 18–29% less time, encoding about 9% less. The changelog says about 25% and 10%.