[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:
                                                 |  adamsilverstein
     Type:  defect (bug)                         |      Status:  reopened
 Priority:  normal                               |   Milestone:  6.8.2
Component:  Media                                |     Version:  6.8
 Severity:  critical                             |  Resolution:
 Keywords:  has-patch has-test-info has-unit-    |     Focuses:
  tests changes-requested                        |
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Comment (by siliconforks):

 I've been checking the results of resizing when using the `png8` format
 and I've noticed some quality issues with it.  `quantizeImage` seems to
 give better quality.

 A good example of this is the image from #63481 - for some reason,
 ImageMagick seems to reduce the number of colors when resizing and saving
 in `png8` format.  This does not happen when using `quantizeImage`, and
 the final quality seems much better.  (Admittedly, the `png8` version has
 a smaller file size, presumably since it has fewer colors.  But they are
 both saved in indexed format, and they are both smaller than the full-size
 image, which was what the original goal was in fixing #36477.  I don't
 think any further reduction in file size is worthwhile if it means a big
 loss in quality.)

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Ticket URL: <https://core.trac.wordpress.org/ticket/63448#comment:86>
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