[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 dev-         |     Focuses:
  feedback has-unit-tests commit fixed-major     |
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Comment (by SirLouen):

 Replying to [comment:76 siliconforks]:
 > I would think it would be fine to call `quantizeImage( 256, ... )` with
 the number 256 just a hard-coded fixed value, unless someone knows of an
 image where that doesn't work well for some reason...?

 So the last bit for me would be finding out a way to spot alpha channels
 confidently.

 If alpha channels spotting work for example say after ImageMagick version
 7.0+, we could always suggest a dev note with a warning like: "If you
 image after resizing is losing gradients, please update your ImageMagick
 version". Although from what I read, it was only a Q16 trouble that
 affected all versions across.

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Ticket URL: <https://core.trac.wordpress.org/ticket/63448#comment:77>
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