[wp-trac] [WordPress Trac] #40415: Imagick resize filter hook

[WordPress Trac]

#40415: Imagick resize filter hook
-------------------------+-----------------------------
 Reporter:  virgodesign  |      Owner:
     Type:  enhancement  |     Status:  new
 Priority:  normal       |  Milestone:  Awaiting Review
Component:  Media        |    Version:  4.7.3
 Severity:  normal       |   Keywords:
  Focuses:               |
-------------------------+-----------------------------
 As of ticket #33642, Wordpress 4.5 introduces the `thumbnail_image()`
 function within the `WP_Image_Editor_Imagick` class.
 This function uses the default imagick filter `FILTER_TRIANGLE` to assists
 the image resizing process.
 Within the `thumbnail_image()` is even declared a list of allowed filters
 that actually are absolute unsued due to the fact that wordpress uses only
 the default filter `FILTER_TRIANGLE`. The filter list is

 {{{
 'FILTER_POINT'
 'FILTER_BOX'
 'FILTER_TRIANGLE'
 'FILTER_HERMITE'
 'FILTER_HANNING'
 'FILTER_HAMMING'
 'FILTER_BLACKMAN'
 'FILTER_GAUSSIAN'
 'FILTER_QUADRATIC'
 'FILTER_CUBIC'
 'FILTER_CATROM'
 'FILTER_MITCHELL'
 'FILTER_LANCZOS'
 'FILTER_BESSEL'
 'FILTER_SINC'
 }}}

 Resizing image using the default filter often gives as a result a softly
 blurry thumbnail image. this blur effect became more visible as the
 thumbnail size increase.

 Using filter like `FILTER_HAMMING` or `FILTER_SINC` the blur effect
 disappear, giving a great resizing result.

 To better improve the use of the resizing process and to give any users
 the ability to choose which type of filter to use, I think that could be
 implemented the following filter hook:

 {{{
 $filter_name = apply_filters('image_resize_filter', $filter_name);
 }}}

 that will give an opportunity to change this filter before the resizing
 process will perform.
 This filter should be implemented at the beginning (line 1) of the
 `thumbnail_image()` function.
 This way everyone can, optionally, change the imagick resize filter
 easily.

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Ticket URL: <https://core.trac.wordpress.org/ticket/40415>
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