[wp-trac] [WordPress Trac] #45982: PDF thumbnails have a default black background

[WordPress Trac]

#45982: PDF thumbnails have a default black background
--------------------------+------------------------------
 Reporter:  nebrekab      |       Owner:  (none)
     Type:  defect (bug)  |      Status:  new
 Priority:  normal        |   Milestone:  Awaiting Review
Component:  Media         |     Version:  5.0.3
 Severity:  normal        |  Resolution:
 Keywords:                |     Focuses:
--------------------------+------------------------------

Comment (by jlambe):

 I was facing this exact same issue recently but it seems there is an easy
 fix for this by providing your own editor class that extends the core
 `WP_Image_Editor_Imagick` class. You can hook into the `wp_image_editors`
 filter and add your editor class as the first one from the list.

 Here is an example of a working solution.

 First, create a custom editor class that extends the imagick core class:

 {{{#!php
 <?php

 namespace App\Cms\Media\Editors;

 final class ExtendedWpImageEditorImagick extends \WP_Image_Editor_Imagick
 {
     protected function pdf_load_source()
     {
         $loaded = parent::pdf_load_source();

         try {
 $this->image->setImageAlphaChannel(\Imagick::ALPHACHANNEL_REMOVE);
             $this->image->setBackgroundColor('white');
         } catch (\Exception $exception) {
             error_log($exception->getMessage());
         }

         return $loaded;
     }
 }

 }}}

 Next hook into the filter and set your editor as the first implementation
 like so:

 {{{#!php
 <?php
 add_filter('wp_image_editors', function (array $editors) {
     array_unshift($editors, ExtendedWpImageEditorImagick::class);

     return $editors;
 });
 }}}


 In my example, I was able to remove the transparent alpha channel of our
 PDFs to help generate a preview image with a white background. I've
 overwritten the `pdf_load_source` method but you can override any other
 method based on your needs.

 I hope this can also help. It's not that I'm against a hook for background
 color property only but perhaps a more generic hook to get the
 `$this->image` instance from the imagick core editor would be useful. At
 least where we're sure it is correctly loaded. In the meantime, the
 solution above can help people customize the behavior without touching to
 the core files for their project.

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Ticket URL: <https://core.trac.wordpress.org/ticket/45982#comment:16>
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