[wp-trac] [WordPress Trac] #15989: image_resize_dimensions() mistakenly defaults crop center as image's center of gravity.

[WordPress Trac]

#15989: image_resize_dimensions() mistakenly defaults crop center as image's center
of gravity.
-------------------------+-------------------------------------------------
 Reporter:  jacof        |      Owner:
     Type:  defect       |     Status:  new
  (bug)                  |  Milestone:  Awaiting Review
 Priority:  normal       |    Version:  3.1
Component:  Post         |   Keywords:  Thumbnails, Resizing, Rescaling,
  Thumbnails             |  Cropping
 Severity:  major        |
-------------------------+-------------------------------------------------
 WordPress add_image_size() routine calls ultimately for
 image_resize_dimensions(), which calculates the cropped image dimensions.
 (http://core.trac.wordpress.org/browser/tags/3.0.3/wp-
 includes/media.php#L333)

 The function assumes that the cropping center is always the gravity center
 of the image, whereas the user must be able to select where and how the
 cropping will be made.

 {{{
 $s_x = floor( ($orig_w - $crop_w) / 2 );
 $s_y = floor( ($orig_h - $crop_h) / 2 );
 }}}

 Due to this, custom thumbnails result cropped around wrong centers.

 WordPress' Editor inside the Multimedia dialog doesn't affect post
 thumbnails defined by the user's theme, but only the thumbnails defined in
 the admin, as it doesn't regenerate them after rescaling the image. A
 temporary fix is regenerating all of the thumbnails using a third party
 plugin ("Regenerate Post Thumbnails"). This temporary fix generates
 (#Thumbs)*(#Images)*(#Resizes)+(#Images) in the Server, which is over
 demanding.

 Fixing the Wordpress Editor to affect post-thumbnails (as it should) would
 not be a proper fix, since the user must not be constrained to reducing
 the dimensions of his/her image as a whole in order to produce a correct
 thumbnail.

 The two solutions feasable for this are:

 1- Correct the Wordpress Multimedia Editor to regenerate thumbnails after
 rescaling the image (short-term).

 2- Modify image_resize_dimensions() to accept optional $x=0, $y=0 and
 allowing, ultimately, the selection of those values in the Multimedia
 Editor by the user, for each image, and for each thumbnail.

-- 
Ticket URL: <http://core.trac.wordpress.org/ticket/15989>
WordPress Trac <http://core.trac.wordpress.org/>
WordPress blogging software