Changeset 59589 for trunk/src/wp-includes/class-wp-image-editor-imagick.php

Timestamp:

01/07/2025 10:33:37 PM (16 months ago)

Author:

adamsilverstein

Message:

Media: improve Imagick handling of colors and alpha channel for PNG image uploads.

Fix an issue where index color (8 bit) PNG uploads were output as true color (24 bit) PNGs, significantly increasing their size. When using Imagick, PNG output images will now match the colors of the uploaded image.

Also, correct handling of PNG alpha channel information so it is preserved in output images.

Props adamsilverstein, pbearne, nosilver4u, peterdavehello, joemcgill, azaozz, codex-m, kirasong, justlevine, jokanane, sallyruchman, wpfed, tgsrvrs, antpb, tb1909.
Fixes #36477.

File:

• trunk/src/wp-includes/class-wp-image-editor-imagick.php (modified) (1 diff)

trunk/src/wp-includes/class-wp-image-editor-imagick.php

@@ -485 +485 @@
                 $this->image->setOption( 'png:compression-level', '9' );
                 $this->image->setOption( 'png:compression-strategy', '1' );
-                $this->image->setOption( 'png:exclude-chunk', 'all' );
+                // Check to see if a PNG is indexed, and find the pixel depth.
+                if ( is_callable( array( $this->image, 'getImageDepth' ) ) ) {
+                    $indexed_pixel_depth = $this->image->getImageDepth();
+
+                    // Indexed PNG files get some additional handling.
+                    if ( 0 < $indexed_pixel_depth && 8 >= $indexed_pixel_depth ) {
+                        // Check for an alpha channel.
+                        if (
+                            is_callable( array( $this->image, 'getImageAlphaChannel' ) )
+                            && $this->image->getImageAlphaChannel()
+                        ) {
+                            $this->image->setOption( 'png:include-chunk', 'tRNS' );
+                        } else {
+                            $this->image->setOption( 'png:exclude-chunk', 'all' );
+                        }
+
+                        // Reduce colors in the images to maximum needed, using the global colorspace.
+                        $max_colors = pow( 2, $indexed_pixel_depth );
+                        if ( is_callable( array( $this->image, 'getImageColors' ) ) ) {
+                            $current_colors = $this->image->getImageColors();
+                            $max_colors = min( $max_colors, $current_colors );
+                        }
+                        $this->image->quantizeImage( $max_colors, $this->image->getColorspace(), 0, false, false );
+
+                        /**
+                         * If the colorspace is 'gray', use the png8 format to ensure it stays indexed.
+                         */
+                        if ( Imagick::COLORSPACE_GRAY === $this->image->getImageColorspace() ) {
+                            $this->image->setOption( 'png:format', 'png8' );
+                        }
+                    }
+                }
             }