posts: fix incorrect exif rotation for PNGs.

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Fix a bug where where PNG images could be incorrectly detected as
exif-rotated. This would happen when a PNG contained the
IFD0:Orientation flag. It's technically possible for a PNG to contain
this flag, but it's ignored by libvips and by browsers.

post #3762340 (nsfw) is an example of a PNG like this.

The fix is to use `autorot` to let libvips apply the rotation instead of
trying to interpret the exif data ourselves. Note that libvips-8.9 has a
bug where it doesn't strip the orientation flag after applying
`autorot`, which leads to the image being incorrectly rotated a second
time when generating the thumbnail. Use libvips-8.11 instead.

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This commit is contained in:

evazion

2021-09-22 22:48:44 -05:00

parent 9c0ab258cb

commit 74b03a7bd0

5 changed files with 24 additions and 20 deletions

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