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LibGfx: Use PNG::paeth_predictor() in png decoding path

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Increases code reuse between encoder and decoder a tiny bit.
No behavior change.

(We should use the vectorized version in the future! But first,
we should learn to do the prediction in-place.)
This commit is contained in:
Nico Weber 2023-11-16 19:26:26 -05:00 committed by Andreas Kling
parent 2763fb45f7
commit 6b2c60404d
Notes: sideshowbarker 2024-07-17 00:49:59 +09:00 
Author: https://github.com/nico
Commit: https://github.com/SerenityOS/serenity/commit/6b2c60404d
Pull-request: https://github.com/SerenityOS/serenity/pull/21966
1 changed files with 1 additions and 13 deletions
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14
Userland/Libraries/LibGfx/ImageFormats/PNGLoader.cpp
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@ -325,19 +325,7 @@ static void unfilter_scanline(PNG::FilterType filter, Bytes scanline_data, Reado
u8 left = (i < bytes_per_complete_pixel) ? 0 : scanline_data[i - bytes_per_complete_pixel];
u8 above = previous_scanlines_data[i];
u8 upper_left = (i < bytes_per_complete_pixel) ? 0 : previous_scanlines_data[i - bytes_per_complete_pixel];
i32 predictor = left + above - upper_left;
u32 predictor_left = abs(predictor - left);
u32 predictor_above = abs(predictor - above);
u32 predictor_upper_left = abs(predictor - upper_left);
u8 nearest;
if (predictor_left <= predictor_above && predictor_left <= predictor_upper_left) {
nearest = left;
} else if (predictor_above <= predictor_upper_left) {
nearest = above;
} else {
nearest = upper_left;
}
scanline_data[i] += nearest;
scanline_data[i] += PNG::paeth_predictor(left, above, upper_left);
}
break;
default: