Fill identical pixels with transparency in subsequent frames when saving GIF #7568
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This was referenced Dec 24, 2023
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Could this be causing the |
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Yes, this would be the cause - but rather than just undoing this change, it would be better to adjust it, to both reduce filesize and to fix your problem. The quickest way of understanding how to do that would be for you to post a self-contained example of your problem in that issue. |
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When saving multiple GIF frames, Pillow trims identical edges of each new frame. This PR goes further, setting the pixels that are not new in the next frame as transparent if Pillow is optimizing. If there is no transparency, try and allocate one.
I started work on this after seeing #6832 (comment). If I remove
optimize=Falsefrom that code, then without this change the file size is 21.5mb. With this change, the file size is 8.1mb.For a less dramatic example, the output of #617 (comment) is reduced from 408kb to 345kb
Because the only difference in output should be filesize, there are no new tests to demonstrate correctness. I have added a test to cover an exception caught if trying to add transparency when there is no room in the frame.