[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       |  Resolution:
 Keywords:               |     Focuses:
-------------------------+------------------------------

Comment (by dpacmittal):

 +1 for this. Triangle is a really bad default filter. WP should provide a
 filter hook, or better default.

 In the meanwhile I'm using this workaround:
 in your functions.php:
 {{{#!php
 <?php
 require_once('class-imagick-modded.php');
 if(class_exists('WP_Image_Editor_Imagick_Modded')){
     // Force imagick modded
     add_filter('wp_image_editors', function($implementations){
     return ['WP_Image_Editor_Imagick_Modded'];
     })
 }
 }}}

 class-imagick-modded.php:
 {{{#!php
 <?php
 <?php
 /**
  * WordPress Imagick Image Editor
  *
  * @package WordPress
  * @subpackage Image_Editor
  */

 /**
  * WordPress Image Editor Class for Image Manipulation through Imagick PHP
 Module
  *
  * @since 3.5.0
  *
  * @see WP_Image_Editor
  */

 if(!class_exists('WP_Image_Editor_Imagick'))
     return;
 class WP_Image_Editor_Imagick_Modded extends WP_Image_Editor_Imagick {
 /**
      * Efficiently resize the current image
      *
      * This is a WordPress specific implementation of
 Imagick::thumbnailImage(),
      * which resizes an image to given dimensions and removes any
 associated profiles.
      *
      * @since 4.5.0
      *
      * @param int    $dst_w       The destination width.
      * @param int    $dst_h       The destination height.
      * @param string $filter_name Optional. The Imagick filter to use when
 resizing. Default 'FILTER_TRIANGLE'.
      * @param bool   $strip_meta  Optional. Strip all profiles, excluding
 color profiles, from the image. Default true.
      * @return bool|WP_Error
      */
     protected function thumbnail_image( $dst_w, $dst_h, $filter_name =
 'FILTER_HAMMING', $strip_meta = true ) {
         $allowed_filters = array(
             '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',
         );

         /**
          * Set the filter value if '$filter_name' name is in our whitelist
 and the related
          * Imagick constant is defined or fall back to our default filter.
          */
         if ( in_array( $filter_name, $allowed_filters ) && defined(
 'Imagick::' . $filter_name ) ) {
             $filter = constant( 'Imagick::' . $filter_name );
         } else {
             $filter = defined( 'Imagick::FILTER_HAMMING' ) ?
 Imagick::FILTER_HAMMING : false;
         }

         /**
          * Filters whether to strip metadata from images when they're
 resized.
          *
          * This filter only applies when resizing using the Imagick editor
 since GD
          * always strips profiles by default.
          *
          * @since 4.5.0
          *
          * @param bool $strip_meta Whether to strip image metadata during
 resizing. Default true.
          */
         if ( apply_filters( 'image_strip_meta', $strip_meta ) ) {
             $this->strip_meta(); // Fail silently if not supported.
         }

         try {
             /*
              * To be more efficient, resample large images to 5x the
 destination size before resizing
              * whenever the output size is less that 1/3 of the original
 image size (1/3^2 ~= .111),
              * unless we would be resampling to a scale smaller than
 128x128.
              */
             if ( is_callable( array( $this->image, 'sampleImage' ) ) ) {
                 $resize_ratio  = ( $dst_w / $this->size['width'] ) * (
 $dst_h / $this->size['height'] );
                 $sample_factor = 5;

                 if ( $resize_ratio < .111 && ( $dst_w * $sample_factor >
 128 && $dst_h * $sample_factor > 128 ) ) {
                     $this->image->sampleImage( $dst_w * $sample_factor,
 $dst_h * $sample_factor );
                 }
             }
             /*
              * Use resizeImage() when it's available and a valid filter
 value is set.
              * Otherwise, fall back to the scaleImage() method for
 resizing, which
              * results in better image quality over resizeImage() with
 default filter
              * settings and retains backward compatibility with pre 4.5
 functionality.
              */
             if ( is_callable( array( $this->image, 'resizeImage' ) ) &&
 $filter ) {
                 $this->image->setOption( 'filter:support', '2.0' );
                 $this->image->resizeImage( $dst_w, $dst_h, $filter, 1 );
             } else {
                 $this->image->scaleImage( $dst_w, $dst_h );
             }

             // Set appropriate quality settings after resizing.
             if ( 'image/jpeg' == $this->mime_type ) {

                     $this->image->unsharpMaskImage( 0.25, 0.25, 8, 0.065
 );
                 }

                 $this->image->setOption( 'jpeg:fancy-upsampling', 'off' );
             }

             if ( 'image/png' === $this->mime_type ) {
                 $this->image->setOption( 'png:compression-filter', '5' );
                 $this->image->setOption( 'png:compression-level', '9' );
                 $this->image->setOption( 'png:compression-strategy', '1'
 );
                 $this->image->setOption( 'png:exclude-chunk', 'all' );
             }

             /*
              * If alpha channel is not defined, set it opaque.
              *
              * Note that Imagick::getImageAlphaChannel() is only available
 if Imagick
              * has been compiled against ImageMagick version 6.4.0 or
 newer.
              */
             if ( is_callable( array( $this->image, 'getImageAlphaChannel'
 ) )
                 && is_callable( array( $this->image,
 'setImageAlphaChannel' ) )
                 && defined( 'Imagick::ALPHACHANNEL_UNDEFINED' )
                 && defined( 'Imagick::ALPHACHANNEL_OPAQUE' )
             ) {
                 if ( $this->image->getImageAlphaChannel() ===
 Imagick::ALPHACHANNEL_UNDEFINED ) {
                     $this->image->setImageAlphaChannel(
 Imagick::ALPHACHANNEL_OPAQUE );
                 }
             }

             // Limit the bit depth of resized images to 8 bits per
 channel.
             if ( is_callable( array( $this->image, 'getImageDepth' ) ) &&
 is_callable( array( $this->image, 'setImageDepth' ) ) ) {
                 if ( 8 < $this->image->getImageDepth() ) {
                     $this->image->setImageDepth( 8 );
                 }
             }

             if ( is_callable( array( $this->image, 'setInterlaceScheme' )
 ) && defined( 'Imagick::INTERLACE_NO' ) ) {
                 $this->image->setInterlaceScheme( Imagick::INTERLACE_NO );
             }
         } catch ( Exception $e ) {
             return new WP_Error( 'image_resize_error', $e->getMessage() );
         }
     }
 }
 }}}

--
Ticket URL: <https://core.trac.wordpress.org/ticket/40415#comment:1>
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