id	summary	reporter	owner	description	type	status	priority	milestone	component	version	severity	resolution	keywords	cc
21668	WordPress still does not save jpeg as progressive jpeg	_ck_		"Every time WordPress does `imagejpeg` it should be doing `imageinterlace` beforehand to set progressive mode, but it's not.

http://php.net/manual/en/function.imageinterlace.php

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`  
`
imageinterlace($newimage,1);
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.
"	enhancement	new	normal	Awaiting Review	Media	3.4.1	normal		has-patch needs-testing	japh@… mike.schroder@… dennen@…