[wp-trac] [WordPress Trac] #36477: Responsive images (srcset) can include images larger than the full size

[WordPress Trac]

#36477: Responsive images (srcset) can include images larger than the full size
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 Reporter:  peterdavehello                       |       Owner:  pbearne
     Type:  defect (bug)                         |      Status:  assigned
 Priority:  normal                               |   Milestone:  Future
                                                 |  Release
Component:  Media                                |     Version:  4.4.2
 Severity:  normal                               |  Resolution:
 Keywords:  has-patch needs-testing dev-         |     Focuses:
  feedback has-unit-tests                        |  performance
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Comment (by nosilver4u):

 I've been working on a fix for this in EWWW Image Optimizer, and pretty
 sure it has not been fixed. I have multiple paletted PNG images that have
 thumbs much larger than the original. I would note, checking that an image
 is 8-bit is not sufficient, one needs to make sure it is also paletted
 (PNG color type 3).
 I am definitely curious if your fix works though, as I've tried a couple
 other pure-PHP fixes: quantizing and/or prefixing the filename with
 'PNG8:'. The former introduces some ugly "noise" around transparent
 boundaries, and the latter just flat-out failed for me on both IM 6.9 and
 7.1.
 Because EWWW IO has pngquant available (or an image-processing API), I
 ended up using pngquant to reduce the palette accordingly, and that worked
 very nicely.

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Ticket URL: <https://core.trac.wordpress.org/ticket/36477#comment:49>
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