[wp-trac] [WordPress Trac] #63448: Image quality significantly degrades for resized PNGs with transparency in WordPress 6.8.1

[WordPress Trac]

#63448: Image quality significantly degrades for resized PNGs with transparency in
WordPress 6.8.1
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 Reporter:  elvismdev     |       Owner:  (none)
     Type:  defect (bug)  |      Status:  new
 Priority:  normal        |   Milestone:  6.8.2
Component:  Media         |     Version:  6.8
 Severity:  major         |  Resolution:
 Keywords:  has-patch     |     Focuses:
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Comment (by elvismdev):

 Thanks @wildworks for digging deep into this and pinpointing the
 regression to the `quantizeImage()` line added in [59589].

 From my testing and what others have also reported, this function seems to
 reduce image quality drastically, particularly for:

 * PNGs with transparency or soft gradients
 * Images with smooth color transitions, like illustrations or UI graphics

 From my research this seems to be because `quantizeImage()` limits the
 color palette used in the resized image. While useful for reducing file
 size, it's too aggressive by default in these cases, leading to color
 banding and a loss of visual fidelity.

 I'm adding a patch via this [https://github.com/WordPress/wordpress-
 develop/pull/8810 GitHub PR #8810] that skips quantization unless
 `$max_colors < 256`, which is common when intentional palette reduction is
 desired.

 Would love feedback from others affected by this, and happy to iterate
 further if needed.

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Ticket URL: <https://core.trac.wordpress.org/ticket/63448#comment:9>
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