PHP圖片壓縮

public function image_compression($url)
{
    $real_path = $_SERVER['DOCUMENT_ROOT'] . $url;
    list($width, $height, $type) = getimagesize($real_path);
    $proportion = $height / $width;
    $new_width  = ($width > 800 ? 800 : $width) * 0.9;
    $new_height = $new_width * $proportion;
    switch ($type) {
        case 1:
            $is_gif = $this->is_gif($real_path);
            if ($is_gif) {
                header('Content-Type:image/gif');
                $image_wp = imagecreatetruecolor($new_width, $new_height);
                $image    = imagecreatefromgif($real_path);
                imagecopyresampled($image_wp, $image, 0, 0, 0, 0, $new_width, $new_height, $width, $height);
                imagejpeg($image_wp, $real_path, 75);
                imagedestroy($image_wp);
            }
            break;
        case 2:
            header('Content-Type:image/jpeg');
            $image_wp = imagecreatetruecolor($new_width, $new_height);
            $image    = imagecreatefromjpeg($real_path);
            imagecopyresampled($image_wp, $image, 0, 0, 0, 0, $new_width, $new_height, $width, $height);
            imagejpeg($image_wp, $real_path, 75);
            imagedestroy($image_wp);
            break;
        case 3:
            header('Content-Type:image/png');
            $image_wp = imagecreatetruecolor($new_width, $new_height);
            $image    = imagecreatefrompng($real_path);
            imagecopyresampled($image_wp, $image, 0, 0, 0, 0, $new_width, $new_height, $width, $height);
            imagejpeg($image_wp, $real_path, 75);
            imagedestroy($image_wp);
            break;
    }
}

function is_gif($path)
{
    $fp         = fopen($path, 'rb');
    $image_head = fread($fp, 1024);
    fclose($fp);
    return preg_match("/" . chr(0x21) . chr(0xff) . chr(0x0b) . 'NETSCAPE2.0' . "/", $image_head) ? false : true;
}