Changeset 60246

Timestamp:

05/22/2025 09:38:22 PM (2 months ago)

Author:

adamsilverstein

Message:

Media: fix degraded handling for 24 bit PNG uploads.

Add additional logic to correctly identify indexed PNG images so output PNGs correctly match the uploaded image depth.

Fix a regression introduced in WordPress 6.8 [59589] where uploaded Truecolor PNG images (meaning > 8 bit) were mis-identified as indexed (8 bit) images, causing output images to be indexed instead of Truecolor resulting in a noticeable visual degradation.

Props elvismdev, wildworks, SirLouen, siliconforks, joemcgill, iamshashank, nosilver4u.
Fixes #63448.

Location:

trunk

Files:

• src/wp-includes/class-wp-image-editor-imagick.php (modified) (1 diff)
• tests/phpunit/data/images/png-tests/grayscale-test-image.png (added)
• tests/phpunit/data/images/png-tests/vivid-green-bird.png (added)
• tests/phpunit/tests/image/editorImagick.php (modified) (4 diffs)

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' );
-                // 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' );
-                        }
+
+                // Indexed PNG files get some additional handling.
+                // See #63448 for details.
+                if (
+                    is_callable( array( $this->image, 'getImageProperty' ) )
+                    && '3' === $this->image->getImageProperty( 'png:IHDR.color-type-orig' )
+                ) {
+
+                    // 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' );
                     }
+                    // Set the image format to Indexed PNG.
+                    $this->image->setOption( 'png:format', 'png8' );
+
+                } else {
+                    $this->image->setOption( 'png:exclude-chunk', 'all' );
                 }
             }

trunk/tests/phpunit/tests/image/editorImagick.php

@@ -771 +771 @@
      *
      * @dataProvider data_resizes_are_small_for_16bit_images
+     *
+     * @param string $file Path to the image file.
      */
     public function test_resizes_are_small_for_16bit_images( $file ) {
@@ -784 +786 @@
         $imagick_image_editor->resize( $size['width'] * .5, $size['height'] * .5 );
 
-        $saved = $imagick_image_editor->save( $temp_file );
+        $imagick_image_editor->save( $temp_file );
 
         $new_filesize = filesize( $temp_file );
@@ -794 +796 @@
 
     /**
-     * data_test_resizes_are_small_for_16bit
+     * Data provider for test_resizes_are_small_for_16bit_images.
      *
      * @return array[]
@@ -817 +819 @@
         );
     }
+
+    /**
+     * Tests that the 'png:IHDR.color-type-orig' property is preserved after resizing
+     * Used to identify indexed PNG images, see https://www.w3.org/TR/PNG-Chunks.html#C.IHDR.
+     *
+     * @ticket 63448
+     * @dataProvider data_png_color_type_after_resize
+     *
+     * @param string $file_path             Path to the image file.
+     * @param int    $expected_color_type   The expected original color type.
+     */
+    public function test_png_color_type_is_preserved_after_resize( $file_path, $expected_color_type ) {
+
+        $temp_file = DIR_TESTDATA . '/images/test-temp.png';
+
+        $imagick_image_editor = new WP_Image_Editor_Imagick( $file_path );
+        $imagick_image_editor->load();
+
+        $size = $imagick_image_editor->get_size();
+        $imagick_image_editor->resize( $size['width'] * 0.5, $size['height'] * 0.5 );
+        $imagick_image_editor->save( $temp_file );
+
+        $imagick           = new Imagick( $temp_file );
+        $actual_color_type = $imagick->getImageProperty( 'png:IHDR.color-type-orig' );
+
+        unlink( $temp_file );
+
+        $this->assertSame( (string) $expected_color_type, $actual_color_type, "The PNG original color type should be preserved after resize for {$file_path}." );
+    }
+
+    /**
+     * Data provider for test_png_color_type_is_preserved_after_resize.
+     *
+     * @return array[]
+     */
+    public static function data_png_color_type_after_resize() {
+        return array(
+            'vivid-green-bird_color_type_6'         => array(
+                DIR_TESTDATA . '/images/png-tests/vivid-green-bird.png',
+                6, // RGBA.
+            ),
+            'grayscale-test-image_color_type_4'     => array(
+                DIR_TESTDATA . '/images/png-tests/grayscale-test-image.png',
+                4, // Grayscale with Alpha.
+            ),
+            'rabbit-time-paletted-or8_color_type_3' => array(
+                DIR_TESTDATA . '/images/png-tests/rabbit-time-paletted-or8.png',
+                3, // Paletted.
+            ),
+            'test8_color_type_3'                    => array(
+                DIR_TESTDATA . '/images/png-tests/test8.png',
+                3, // Paletted.
+            ),
+        );
+    }
 }