Changeset 56271

Timestamp:

07/19/2023 10:33:47 PM (17 months ago)

Author:

antpb

Message:

Media: Adjust PDF upload handling to remove non-opaque alpha channels from previews.

Previously, Imagick uploads of PDF files with non-opaque alpha channels would result in a black background replacing alpha in the generated thumbnail. This patch adds a remove_pdf_alpha_channel() function in the Imagick classes to use a white background instead.

Props gitlost, joemcgill, joedolson, launchinteractive, emirpprime, mwtsn, ceer, maysi, madejackson, 6adminit, costdev, oglekler.
Fixes #39216.

Location:

trunk

Files:

• src/wp-includes/class-wp-image-editor-imagick.php (modified) (2 diffs)
• tests/phpunit/data/images/test-alpha.pdf (added)
• tests/phpunit/tests/image/editorImagick.php (modified) (1 diff)

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

@@ -169 +169 @@
             }
 
+            if ( 'pdf' === $file_extension ) {
+                $this->remove_pdf_alpha_channel();
+            }
+
             $this->mime_type = $this->get_mime_type( $this->image->getImageFormat() );
         } catch ( Exception $e ) {
@@ -753 +757 @@
 
     /**
+     * Removes PDF alpha after it's been read.
+     *
+     * @since 6.4.0
+     */
+    protected function remove_pdf_alpha_channel() {
+        $version = Imagick::getVersion();
+        // Remove alpha channel if possible to avoid black backgrounds for Ghostscript >= 9.14. RemoveAlphaChannel added in ImageMagick 6.7.5.
+        if ( $version['versionNumber'] >= 0x675 ) {
+            try {
+                // Imagick::ALPHACHANNEL_REMOVE mapped to RemoveAlphaChannel in PHP imagick 3.2.0b2.
+                $this->image->setImageAlphaChannel( defined( 'Imagick::ALPHACHANNEL_REMOVE' ) ? Imagick::ALPHACHANNEL_REMOVE : 12 );
+            } catch ( Exception $e ) {
+                return new WP_Error( 'pdf_alpha_process_failed', $e->getMessage() );
+            }
+        }
+    }
+
+    /**
      * @since 3.5.0
      * @since 6.0.0 The `$filesize` value was added to the returned array.

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

@@ -642 +642 @@
         $this->assertNotWPError( $saved );
     }
+
+    /**
+     * Tests that the alpha channel of PDFs is removed from PDF previews.
+     *
+     * Only affects systems with Ghostscript version >= 9.14.
+     *
+     * @ticket 39216
+     *
+     * @covers WP_Image_Editor_Imagick::remove_pdf_alpha_channel
+     */
+    public function test_remove_pdf_alpha_channel_should_remove_the_alpha_channel_in_preview() {
+        if ( ! wp_image_editor_supports( array( 'mime_type' => 'application/pdf' ) ) ) {
+            $this->markTestSkipped( 'Rendering PDFs is not supported on this system.' );
+        }
+
+        $test_file     = DIR_TESTDATA . '/images/test-alpha.pdf';
+        $attachment_id = $this->factory->attachment->create_upload_object( $test_file );
+        $this->assertNotEmpty( $attachment_id, 'The attachment was not created before testing.' );
+
+        $attached_file = get_attached_file( $attachment_id );
+        $this->assertNotEmpty( $attached_file, 'The attached file was not returned.' );
+
+        $rgb = array(
+            'r' => true,
+            'g' => true,
+            'b' => true,
+        );
+
+        // White.
+        $expected = array(
+            'r' => 1,
+            'g' => 1,
+            'b' => 1,
+        );
+
+        $check = image_get_intermediate_size( $attachment_id, 'full' );
+        $this->assertIsArray( $check, 'The intermediate size could not be retrieved.' );
+        $this->assertArrayHasKey( 'file', $check, 'The intermediate size file was not found.' );
+
+        $check_file = path_join( dirname( $attached_file ), $check['file'] );
+        $imagick    = new Imagick( $check_file );
+        $output     = array_map(
+            static function( $value ) {
+                return (int) round( $value );
+            },
+            array_intersect_key( $imagick->getImagePixelColor( 100, 100 )->getColor( true /* normalized */ ), $rgb )
+        );
+        $imagick->destroy();
+        $this->assertSame( $expected, $output, 'The image color of the generated thumb does not match expected opaque background.' ); // Allow for floating point equivalence.
+    }
 }