Enable custom parameters for .webp and .avif thumbnails (#876)

* Enable custom parameters for .webp and .avif thumbnails
The thumbnail code assumed that images are .gif, .png or .jpg, and we defaulted to quality settings for .jpg thumbnails. But for both .avif and .webp, other quality settings are preferable (and possible other additional parameters).

This code changes the code for $serendipity['imagemagick_thumb_parameters'] so that it can be an array, with the image mime type as key and their specific parameters as values. It also sets sane defaults for the gd path for both formats, which also enables thumbnails in both formats when imagemagick is not used.

* Document change

Author: onli

docs/NEWS

@@ -3,6 +3,13 @@ Version 2.6-alpha1 ()
    * Avoid PHP 8 warning about incurrect reference return of db_query
      function
 
+   * Enable .webp and .avif thumbnails also when using PHP's gd module
+     instead of imagemagick. Optimize imagemagick's thumbnail parameters,
+     for smaller filesizes for .webp and .avif images.
+     NOTE: Check the new structure in serendipity_config.inc.php if you
+     have set a custom value for imagemagick_thumb_parameters in your
+     local config file.
+
    * PHP 8.4 fix: Remove deprecated constant E_STRICT
 
    * PHP 8 compatibility fixes for bundled XML/RPC.php

include/functions_images.inc.php

@@ -735,7 +735,22 @@ function serendipity_makeThumbnail($file, $directory = '', $size = false, $thumb
                     $newSize .= '>'; // tell imagemagick to not enlarge small images, only works if safe_mode is off (safe_mode turns > in to \>)
                 }
                 if (!$serendipity['imagemagick_nobang']) $newSize .= '!'; // force the first run image geometry exactly to given sizes, if there were rounding differences (see https://github.com/s9y/Serendipity/commit/94881ba4c0e3bdd4b5fac510e93977e239171c1c and comments)
-                $cmd = escapeshellcmd($serendipity['convert'] . ' ' . $serendipity['imagemagick_thumb_parameters']) . ' -antialias -resize ' . serendipity_escapeshellarg($newSize) . ' ' . serendipity_escapeshellarg($infile) .' '. serendipity_escapeshellarg($outfile);
+
+                $params = '-sampling-factor 4:2:0 -unsharp 0x0.75+0.75+0.008 -strip -quality 85';
+                if (is_string($serendipity['imagemagick_thumb_parameters'])) {
+                    // In s9y < 2.6, $serendipity['imagemagick_thumb_parameters'] was a string and the default
+                    // value targeted jpgs. Users might have set variants of that in their local config, so
+                    // we provide a backwards compatibly path here
+                    $params = $serendipity['imagemagick_thumb_parameters'];
+                } else {
+                    // In 2.6 $serendipity['imagemagick_thumb_parameters'] has values for different
+                    // image formats
+                    if (isset($serendipity['imagemagick_thumb_parameters'][$fdim['mime']])) {
+                        $params = $serendipity['imagemagick_thumb_parameters'][$fdim['mime']];
+                    }
+                }
+                
+                $cmd = escapeshellcmd($serendipity['convert'] . ' ' . $params) . ' -antialias -resize ' . serendipity_escapeshellarg($newSize) . ' ' . serendipity_escapeshellarg($infile) .' '. serendipity_escapeshellarg($outfile);
             }
             exec($cmd, $output, $result);
             if ($result != 0) {
@@ -1318,6 +1333,18 @@ function serendipity_functions_gd($infilename) {
         $func['save'] = 'imagejpeg';
         $func['qual'] = 85;
         break;
+        
+    case 'avif':
+        $func['load'] = 'imagecreatefromavif';
+        $func['save'] = 'imageavif';
+        $func['qual'] = 60;
+        break;
+        
+    case 'webp':
+        $func['load'] = 'imagecreatefromwebp';
+        $func['save'] = 'imagewebp';
+        $func['qual'] = 90;
+        break;
 
     case 'png':
         $func['load'] = 'imagecreatefrompng';

serendipity_config.inc.php

@@ -496,7 +496,10 @@
     // image quality when resizing.
     // 
     // Set a variable like below in your serendpity_config_local.inc.php with your own settings
-    $serendipity['imagemagick_thumb_parameters'] = '-sampling-factor 4:2:0 -unsharp 0x0.75+0.75+0.008 -strip -quality 85 -interlace JPEG';
+    $serendipity['imagemagick_thumb_parameters'] = [ 'image/jpeg' => '-sampling-factor 4:2:0 -unsharp 0x0.75+0.75+0.008 -strip -quality 85 -interlace JPEG',
+                            'image/avif' => '-sampling-factor 4:2:0 -unsharp 0x0.75+0.75+0.008 -strip -quality 60',
+                            'image/webp' => '-sampling-factor 4:2:0 -unsharp 0x0.75+0.75+0.008 -strip -quality 90'
+    ];
 }
 
 serendipity_plugin_api::hook_event('frontend_configure', $serendipity);