PHP图片按等比压缩

/**
        * desription 压缩图片
        * @param sting $imgsrc 图片路径
        * @param string $imgdst 压缩后保存路径
        */
    public function compressedImage($imgsrc, $imgdst) {
        list($width, $height, $type) = getimagesize($imgsrc);
        $new_width = $width; //压缩后的图片宽
        $new_height = $height; //压缩后的图片高
        if ($width >= 600) {
            $per = 600 / $width; //计算比例
            $new_width = $width * $per;
            $new_height = $height * $per;
        }
        switch ($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, $height);
                            //90代表的是质量、压缩图片容量大小
                imagejpeg($image_wp, $imgdst, 90);
                imagedestroy($image_wp);
                imagedestroy($image);
            }
            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, $height);
                     //90代表的是质量、压缩图片容量大小
            imagejpeg($image_wp, $imgdst, 90);
            imagedestroy($image_wp);
            imagedestroy($image);
            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, $height);
                     //90代表的是质量、压缩图片容量大小
            imagejpeg($image_wp, $imgdst, 90);
            imagedestroy($image_wp);
            imagedestroy($image);
            break;
        }
    }