WordPress does not save jpeg as progressive jpeg
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Every time WordPress does imagejpeg it should be doing imageinterlace beforehand to set progressive mode, but it's not.
Progressive jpeg has been supported by ALL browsers since 2001 or so.
progressive demo: http://bbshowcase.org/progressive/
Note that even if an ancient browser is listed somewhere as not rendering progressive, progressive jpeg still will be displayed, simply showing it all at once rather than gradual.
IE6 for example WILL load progressive jpeg, it will just not render it progressively, instead it will load the entire image and then render all at once at the end.
Progressive algorithm will also make slightly smaller jpeg as a side effect in most cases.
ie. in media.php
imagejpeg( $newimage, ...
This update is years overdue.
It might be possible to futureproof this by adding a filter to $newimage before the final imagejpeg. I am uncertain if that would work since filters would not pass $newimage by reference and instead make a copy - while newimage is only a pointer to php/gd memory. Can apply_filters be forced to work somehow by reference instead of a copy? Maybe that should be another feature idea.
Change History (43)
- Keywords 3.7-early added
- Milestone changed from Awaiting Review to Future Release
3 years ago
- Keywords 3.7-early removed
- Milestone changed from Future Release to 3.8
6 months ago
- Summary changed from WordPress still does not save jpeg as progressive jpeg to WordPress does not save jpeg as progressive jpeg