Fix libgd 223: gdImageRotateGeneric() does not properly interpolate #17380
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We port the respective upstream fix[1]. We only run the test against bundled libgd, since external libgd may yield different results. Cf. <libgd/libgd@2b26be8>.
devnexen
approved these changes
Jan 6, 2025
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We port the respective upstream fix[1]. We only run the test against bundled libgd, since external libgd may yield different results.
Cf. libgd/libgd@2b26be8.
Test outputs prior to the fix:
After the fix:
Rather notable difference, even without enlarging. When enlarging with nearest neighbor, one can see that there are only black and white pixels, but no grey pixels (i.e. antialiasing is missing).
I have not ported the relevant part of the follow-up libgd/libgd@6267414; namely the removal of the rounding, since this appears to slightly decrease quality (artifacts noticeable when enlarging with nearest neighbor):
I'll have a closer look at this, but I think this PR is a relevant fix on its own.