[wp-trac] [WordPress Trac] #30402: medium image size may be larger than full image size

[WordPress Trac]

#30402: medium image size may be larger than full image size
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 Reporter:  qdinar        |       Owner:
     Type:  defect (bug)  |      Status:  new
 Priority:  normal        |   Milestone:  Awaiting Review
Component:  Media         |     Version:  3.9.2
 Severity:  normal        |  Resolution:
 Keywords:  needs-patch   |     Focuses:
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Comment (by dnewton):

 This isn't a problem that's unique to WordPress (or ImageMagick); it also
 happens with Photoshop, etc. I've been doing [https://github.com/nwtn
 /image-resize-tests a bunch of tests] to try to find better ways to resize
 images, and this is not an atypical result. See [https://github.com/nwtn
 /image-resize-tests/blob/master/wordpress-comparison.md this comparison
 between WordPress, Photoshop, and some of my test data].

 Basically, when the images are resized there's some smoothing/aliasing
 that happens, which results in colours that weren't in the original. More
 colours = bigger file size. One possible way to handle this in WP could be
 to do the normal resize, check if it's bigger than the original and, if
 so, do another resize with more aggressive (or any in the case of PNGs)
 compression.

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Ticket URL: <https://core.trac.wordpress.org/ticket/30402#comment:4>
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