Ticket #39216: 39216.4.patch

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

@@ -164 +164 @@
                         if ( is_callable( array( $this->image, 'setIteratorIndex' ) ) )
                                 $this->image->setIteratorIndex(0);
 
+                        if ( 'pdf' == $file_extension ) {
+                                $this->pdf_process();
+                        }
+
                         $this->mime_type = $this->get_mime_type( $this->image->getImageFormat() );
                 }
                 catch ( Exception $e ) {
@@ -766 +770 @@
                 }
         }
 
+        /**
+         * Process PDF after it's been read.
+         *
+         * @since 4.x
+         * @access protected
+         *
+         * @return void
+         */
+        protected function pdf_process() {
+                $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.
+                                // Value seems to have remained stable at 12 for ImageMagick 6.7.5 to 7.0 (although other AlphaChannelType enum values have changed).
+                                $this->image->setImageAlphaChannel( defined( 'Imagick::ALPHACHANNEL_REMOVE' ) ? Imagick::ALPHACHANNEL_REMOVE : 12 );
+                        }
+                        catch ( Exception $e ) {
+                                // Ignore.
+                        }
+                }
+        }
 }

tests/phpunit/tests/image/editor_imagick.php

@@ -572 +572 @@
                 unlink( $ret['path'] );
         }
 
+        /**
+         * @ticket 39216
+         * Only affects systems with Ghostscript version >= 9.14.
+         */
+        public function test_remove_alpha_pdf_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 );
+
+                $attached_file = get_attached_file( $attachment_id );
+                $this->assertNotEmpty( $attached_file );
+
+                $rgb = array( 'r' => true, 'g' => true, 'b' => true ); // Used for intersecting - not interested in alpha channel.
+                $expected = array( 'r' => 1, 'g' => 1, 'b' => 1 ); // White.
+
+                $check = image_get_intermediate_size( $attachment_id, 'full' );
+                $this->assertNotEmpty( $check['file'] );
+                $check_file = path_join( dirname( $attached_file ), $check['file'] );
+
+                $imagick = new Imagick( $check_file );
+                $output = array_map( 'round', array_intersect_key( $imagick->getImagePixelColor( 100, 100 )->getColor( true /*normalized*/ ), $rgb ) );
+                $imagick->destroy();
+                $this->assertEquals( $expected, $output ); // Allow for floating point equivalence.
+        }
 }