[wp-trac] [WordPress Trac] #57003: Compress original image upload to avoid uncompressed images

[WordPress Trac]

#57003: Compress original image upload to avoid uncompressed images
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 Reporter:  flixos90     |      Owner:  (none)
     Type:  enhancement  |     Status:  new
 Priority:  normal       |  Milestone:  Awaiting Review
Component:  Media        |    Version:
 Severity:  normal       |   Keywords:  2nd-opinion needs-patch needs-unit-
  Focuses:  performance  |  tests
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 When an image is uploaded to WordPress today, WordPress will generate the
 sub-sized versions using compression with the default quality (e.g. 82 for
 JPEG). The point of this is to offer smaller versions to achieve better
 performance with different viewport sizes. The compression here is a
 significant part of it, as we would not want those smaller sized images to
 be badly compressed and thus overly large in file size.

 A problem (and I would argue oversight) in that approach is that the
 originally uploaded image is still used as is in many cases, even in the
 frontend. #47873 introduced the feature to compress "big" images in a
 smaller version, which makes sense, however that is only part of the
 potential problem here: It can also happen that the original image upload
 is simply an overly large file, even if the dimensions of the image are
 smaller than what makes it qualify for a "big" image.

 This ticket proposes the following:
 * Always generate a new image from the originally uploaded image, even
 when it is not a "big" image (potential exception could be PNGs as
 currently the case, see #48736).
 * Once the image has been generated, compare the file size of the new
 image with the original image:
     * If the new image is smaller, use that one going forward, backing up
 the original image in the same way it already happens as part of the "big"
 image feature.
     * If the new image is larger (i.e. the original was already well
 compressed), delete the new image again and simply keep the original as
 is.

 Given that we already generate an additional image file for "big" image
 uploads, this enhancement would not introduce any concerning overhead. It
 also does not make any assumptions on the original image quality, it
 simply compares the results to make a decision which image to keep. In any
 case, the original image will be kept so it would not be a destructive
 action either.

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Ticket URL: <https://core.trac.wordpress.org/ticket/57003>
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