PHP 圖檔無損壓縮

/**
 * desription 壓縮圖檔
 * @param sting $imgsrc 圖檔路徑
 * @param string $imgdst 壓縮後儲存路徑
 */
function image_zip($imgsrc = '',$imgdst = ''){
    $name = basename($imgsrc);
    if($imgsrc == '' or empty($imgsrc)){
        return '';
    }
  
    if(file_exists($imgdst)){
        return $imgdst;
    }
    list($width,$height,$type) = getimagesize($imgsrc);
    $new_width = $width*1;
    $new_height = $height*1;
    switch($type){
        case 1:
            $giftype=check_gifcartoon($imgsrc);
            if($giftype){
                header('Content-Type:image/gif');
                $image_wp=imagecreatetruecolor($new_width, $new_height);
                $image = imagecreatefromgif($imgsrc);
                imagecopyresampled($image_wp, $image, 0, 0, 0, 0, $new_width, $new_height, $width, $height);
                imagejpeg($image_wp, $imgdst,75);
                imagedestroy($image_wp);
            }
            break;
        case 2:
            header('Content-Type:image/jpeg');
            $image_wp=imagecreatetruecolor($new_width, $new_height);
            $image = imagecreatefromjpeg($imgsrc);
            imagecopyresampled($image_wp, $image, 0, 0, 0, 0, $new_width, $new_height, $width, $height);
            imagejpeg($image_wp, $imgdst,75);
            imagedestroy($image_wp);
            break;
        case 3:
            header('Content-Type:image/png');
            $image_wp=imagecreatetruecolor($new_width, $new_height);
            $image = imagecreatefrompng($imgsrc);
            imagecopyresampled($image_wp, $image, 0, 0, 0, 0, $new_width, $new_height, $width, $height);
            imagejpeg($image_wp, $imgdst,75);
            imagedestroy($image_wp);
            break;
        default:
            header('Content-Type:image/jpg');
            $image_wp=imagecreatetruecolor($new_width, $new_height);
            $image = imagecreatefromjpeg($imgsrc);
            imagecopyresampled($image_wp, $image, 0, 0, 0, 0, $new_width, $new_height, $width, $height);
            imagejpeg($image_wp, $imgdst,75);
            imagedestroy($image_wp);
            break;
    }
    return $imgdst;
}
/**
 * desription 判斷是否gif動畫
 * @param sting $image_file圖檔路徑
 * @return boolean t 是 f 否
 */
function check_gifcartoon($image_file){
    $fp = fopen($image_file,'rb');
    $image_head = fread($fp,1024);
    fclose($fp);
    return preg_match("/".chr(0x21).chr(0xff).chr(0x0b).'NETSCAPE2.0'."/",$image_head)?false:true;
}