[wp-trac] [WordPress Trac] #57238: Criteria for Responsive Images of WebP: Preserve Alpha + Preserve Lossless + Smaller in size than original

[WordPress Trac]

#57238: Criteria for Responsive Images of WebP: Preserve Alpha + Preserve Lossless
+ Smaller in size than original
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 Reporter:  abitofmind       |       Owner:  (none)
     Type:  feature request  |      Status:  new
 Priority:  normal           |   Milestone:  Future Release
Component:  Media            |     Version:
 Severity:  normal           |  Resolution:
 Keywords:                   |     Focuses:
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Changes (by azaozz):

 * version:  6.1.1 =>
 * type:  defect (bug) => feature request
 * milestone:  Awaiting Review => Future Release


Comment:

 Yes, handling/post-processing of WebP images needs improvements.

   Preserve the alpha channel

 Yes, definitely. Note that WebP support alpha transparency with both
 lossless and lossy compression. As far as I see ImageMagick can do that.
 Not sure about GD, probably can.

   Lossless original should result in lossless sized versions → To preserve
 full quality (e.g. screen designs, diagrams, etc)

 Makes sense but perhaps only for images with slammer file size? The
 purpose of image post-processing in WP is to make images "web ready". A
 2MB lossless image is not. If lossy compression can be used to
 significantly reduce the file size without noticeable reduction in
 quality, it should be used imho.

 On the other hand it is pretty rare to see such images. I actually had
 problems finding "real" lossless WebP images to test with (real as in
 specifically crafted that way for use on the web). So not sure if
 implementing this is a priority.

 There are some examples of lossless and lossy compression with alpha
 transparency: https://developers.google.com/speed/webp/gallery2.

   File size of smaller sized versions should never be larger than the
 original

 Yes, of course. This usually applies to images with lossless compression.
 In some cases the sub-sizes of the image may not be created with the same
 settings. For example a sub-size may be created with full colors while the
 original has only 8 bit, etc.

 Related #53663. Also pinging @adamsilverstein who may be interested.

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Ticket URL: <https://core.trac.wordpress.org/ticket/57238#comment:1>
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