[Webkit-unassigned] [Bug 222112] New: WebKit renders APNGs with corrupted palettes

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=222112

            Bug ID: 222112
           Summary: WebKit renders APNGs with corrupted palettes
           Product: WebKit
           Version: Safari 14
          Hardware: iPhone / iPad
               URL: https://omori.wiki/File:MainPage_Battle.png
                OS: iOS 14
            Status: NEW
          Severity: Normal
          Priority: P2
         Component: Images
          Assignee: webkit-unassigned at lists.webkit.org
          Reporter: trashboyjet at gmail.com

Created attachment 420835

  --> https://bugs.webkit.org/attachment.cgi?id=420835&action=review

Test Case Reduction

It appears that WebKit has issues with rendering certain .apng files. I've tested on multiple browsers utilizing WebKit, with a few images, and they generally have corrupted palettes/flickering that does not occur on non-WebKit browsers.

To reproduce this error, simply visit one of the pages attached to this report. It should happen consistently.

By doing the above, you'll see the .apng file flicker or have transparency/palette corruption.

The expected result is to have this function as it does on any non-WebKit browser.

Here's 4 different WebKit browsers I tested on where the issue consistently occurs:
- Safari 14 (macOS)
- Safari 14 (iOS)
- Firefox 31 (iOS)
- Chrome 87.0.4280.77 (iOS)

I've also tested non-WebKit browsers, and the issue isn't present:
- Firefox 85.0.2 (Windows)
- Chrome 88.0.4324.150(Windows)
- Firefox 85.0.1 (macOS)
- Chrome 88.0.4324.182 (macOS)
- Brave 1.19.86 (macOS)

If you need any more information, please let me know.

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