[wp-trac] [WordPress Trac] #18532: resized image dimensions incorrectly floored instead of rounded

[WordPress Trac]

#18532: resized image dimensions incorrectly floored instead of rounded
--------------------------+------------------------------
 Reporter:  _ck_          |       Owner:
     Type:  defect (bug)  |      Status:  new
 Priority:  normal        |   Milestone:  Awaiting Review
Component:  Media         |     Version:  2.5
 Severity:  normal        |  Resolution:
 Keywords:                |
--------------------------+------------------------------
Changes (by scribu):

 * version:   => 2.5


Old description:

> Since WP 2.5 no one has noticed this, not sure if I am surprised.
>
> Image dimensions are incorrectly floored instead of rounded to a proper
> number. Some attempt at "fixup" is done later in some processes to move
> them by a pixel, but still the way it's initially calculated is wrong.
>
> '''For example:
>
> A typical photo has a 3:2 (3/2 = 1.5) ratio.
>
> If it's resized to 600px width, WP will make the height 399px - this is
> wrong.'''
>
> It happens because of ''function wp_constrain_dimensions'' in
> ''media.php'' (~line 304) which floors the float using intval, which is
> wrong.
>

> {{{
>         $w = intval( $current_width  * $ratio );
>         $h = intval( $current_height * $ratio );
> }}}
>
> '''I propose'''
>
> {{{
>         $w = round( $current_width  * $ratio );
>         $h = round( $current_height * $ratio );
> }}}
>
> Earlier in the function, both $ratio and $current_width are already
> handled as numbers, so they have to be valid numbers, no need to use
> intval for that reason, it's just being used to floor, which is bad in
> this case.
>
> Using round is not a performance issue because this function is not used
> in realtime output for templates but typically in admin area.
>
> Optionally while you are at it, put a filter on wp_constrain_dimensions
> and pass the filter all the values passed to the function before the
> array is returned at the end.

New description:

 Image dimensions are incorrectly floored instead of rounded to a proper
 number. Some attempt at "fixup" is done later in some processes to move
 them by a pixel, but still the way it's initially calculated is wrong.

 '''For example:

 A typical photo has a 3:2 (3/2 = 1.5) ratio.

 If it's resized to 600px width, WP will make the height 399px - this is
 wrong.'''

 It happens because of ''function wp_constrain_dimensions'' in
 ''media.php'' (~line 304) which floors the float using intval, which is
 wrong.


 {{{
         $w = intval( $current_width  * $ratio );
         $h = intval( $current_height * $ratio );
 }}}

 '''I propose'''

 {{{
         $w = round( $current_width  * $ratio );
         $h = round( $current_height * $ratio );
 }}}

 Earlier in the function, both $ratio and $current_width are already
 handled as numbers, so they have to be valid numbers, no need to use
 intval for that reason, it's just being used to floor, which is bad in
 this case.

 Using round is not a performance issue because this function is not used
 in realtime output for templates but typically in admin area.

 Optionally while you are at it, put a filter on wp_constrain_dimensions
 and pass the filter all the values passed to the function before the array
 is returned at the end.

--

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Ticket URL: <http://core.trac.wordpress.org/ticket/18532#comment:1>
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