Ticket #2805: wp_create_thumbnail-preserve-PNG-transparency.diff

wp-admin/admin-functions.php

@@ -828 +828 @@
                         }
 
                         $thumbnail = imagecreatetruecolor($image_new_width, $image_new_height);
+
+                        if( $type[2] == 3 and function_exists( 'imagealphablending' ) and function_exists( 'imagesavealpha' ) ) {
+                                // Preserve PNG transparency, from http://php.net/manual/en/function.imagecopyresampled.php#44134
+                                if (function_exists('imageantialias'))
+                                        imageantialias($thumbnail, TRUE); // not necessary, but not always available
+                                imagealphablending($thumbnail, false);
+                                imagesavealpha($thumbnail,true);
+                                $transparent = imagecolorallocatealpha($thumbnail, 255, 255, 255, 0);
+                                for($x=0;$x<$image_new_width;$x++) {
+                                        for($y=0;$y<$image_new_height;$y++) {
+                                                imagesetpixel( $thumbnail, $x, $y, $transparent );
+                                        }
+                                }
+                        }
+
                         @ imagecopyresampled($thumbnail, $image, 0, 0, 0, 0, $image_new_width, $image_new_height, $image_attr[0], $image_attr[1]);
 
                         // If no filters change the filename, we'll do a default transformation.