image cache: send files as content-disposition: attachment; add .png suffix to image urls

classes/handler/public.php

@@ -1051,9 +1051,11 @@ class Handler_Public extends Handler {
 
 		if ($hash) {
 
-			$filename = CACHE_DIR . '/images/' . $hash . '.png';
+			$filename = CACHE_DIR . '/images/' . $hash;
 
 			if (file_exists($filename)) {
+				header("Content-Disposition: attachment; filename=\"".basename($filename)."\"");
+
 				/* See if we can use X-Sendfile */
 				$xsendfile = false;
 				if (function_exists('apache_get_modules') &&

include/functions2.php

@@ -903,13 +903,15 @@
 					$entry->setAttribute('rel', 'noopener noreferrer');
 				}
 
+				if ($entry->nodeName == 'img') {
+
 					if ($entry->hasAttribute('src')) {
 						$src = rewrite_relative_url($site_url, $entry->getAttribute('src'));
 
 						$cached_filename = CACHE_DIR . '/images/' . sha1($src) . '.png';
 
 						if (file_exists($cached_filename)) {
-						$src = SELF_URL_PATH . '/public.php?op=cached_image&hash=' . sha1($src);
+							$src = SELF_URL_PATH . '/public.php?op=cached_image&hash=' . sha1($src) . '.png';
 
 							if ($entry->hasAttribute('srcset')) {
 								$entry->removeAttribute('srcset');
@@ -923,7 +925,6 @@
 						$entry->setAttribute('src', $src);
 					}
 
-				if ($entry->nodeName == 'img') {
 					if ($entry->hasAttribute('src')) {
 						$is_https_url = parse_url($entry->getAttribute('src'), PHP_URL_SCHEME) === 'https';