function createThumbnail($filename, $filename_thumb, $factor) {
                if (file_exists ($filename_thumb)) {
                    if (filemtime($filename) > filemtime($filename_thumb)) $create = TRUE; else $create = FALSE;
                } else $create = TRUE;
                if ($create) {
                    $info = getimagesize($filename);
                    switch ($info[2]) {
                        case IMAGETYPE_JPEG:
                            $image = imagecreatefromjpeg($filename);
                            break;
                        case IMAGETYPE_PNG:
                            $image = imagecreatefrompng($filename);
                            break;
                        case IMAGETYPE_GIF:
                            $image = imagecreatefromgif($filename);
                            break;
                        default: return;
                    }
                    $width_th = intval($info[0] * $factor);
                    $height_th = intval($info[1] * $factor);
                    $imageth = imagecreatetruecolor($width_th, $height_th);
                    imagecopyresampled($imageth, $image, 0, 0, 0, 0,
                        $width_th, $height_th, $info[0], $info[1]);
                    imagejpeg($imageth, $filename_thumb, 100);
                }
            }