make cached image format configuarble through main.cfg

app/modules/cachedimage.php

     public $original;
     public $cache_dir = "tmp/";
     public $default_width = 500;
+    public $format;
+    public $quality;
 
     function __construct($path) {
+        $f3 = \Base::instance();
         $this->original = $path;
+        $this->format = $f3->get('cachedImageFormat') ? : 'jpeg';
+        $this->quality = $f3->get('cachedImageQuality') ? : false;
+        if ($this->quality === false) {
+            switch($this->format) {
+            case 'png':
+                $this->quality = 6;
+                break;
+            case 'jpg':
+            case 'jpeg':
+                $this->quality = 75;
+                break;
+            }
+        }
     }
     
     function get_src($inwidth = 500) {
             $width = $inwidth ? $inwidth : $this->default_width;
             $name = md5($this->original.$width);
         
-            $name =  sprintf("%s_%s.jpg",$fn,$name);
+            $name =  sprintf("%s_%s.%s",$fn,$name,$this->format);
         
             $out = $this->cache_dir.$name;
     
             if(!file_exists($out)) {
                 $img1 = new \Image($this->original);
                 $img1->resize($width);
-                $f3->write($out,$img1->dump('jpeg',75));
+                $f3->write($out,$img1->dump($this->format,$this->quality));
                 unset($img1);
             }
         } else {