PHP生成缩略图

private function create_scaled_image($file_path){
        $file_name = basename($file_path);
        $new_file_path = dirname($file_path) . DIRECTORY_SEPARATOR . $this->thumbnail['upload_dir'] . DIRECTORY_SEPARATOR;
        if(!file_exists($new_file_path))
            @mkdir($new_file_path);
        $new_file_path .= $file_name;
        list($img_width, $img_height) = @getimagesize($file_path);
        if(!$img_width || !$img_height){
            return false;
        }
        $scale = min(
                $this->thumbnail['max_width'] / $img_width, $this->thumbnail['max_height'] / $img_height
        );
        if($scale >= 1){
            if($file_path !== $new_file_path){
                return copy($file_path, $new_file_path);
            }
            return true;
        }
        $new_width = $img_width * $scale;
        $new_height = $img_height * $scale;
        $new_img = @imagecreatetruecolor($new_width, $new_height);
        switch(strtolower(substr(strrchr($file_name, '.'), 1))){
            case 'jpg':
            case 'jpeg':
                $src_img = @imagecreatefromjpeg($file_path);
                $write_image = 'imagejpeg';
                $image_quality = isset($this->thumbnail['jpeg_quality']) ?
                        $this->thumbnail['jpeg_quality'] : 75;
                break;
            case 'gif':
                @imagecolortransparent($new_img, @imagecolorallocate($new_img, 0, 0, 0));
                $src_img = @imagecreatefromgif($file_path);
                $write_image = 'imagegif';
                $image_quality = null;
                break;
            case 'png':
                @imagecolortransparent($new_img, @imagecolorallocate($new_img, 0, 0, 0));
                @imagealphablending($new_img, false);
                @imagesavealpha($new_img, true);
                $src_img = @imagecreatefrompng($file_path);
                $write_image = 'imagepng';
                $image_quality = isset($this->thumbnail['png_quality']) ?
                        $this->thumbnail['png_quality'] : 9;
                break;
            default:
                $src_img = null;
        }
        $success = $src_img && @imagecopyresampled(
                        $new_img, $src_img, 0, 0, 0, 0, $new_width, $new_height, $img_width, $img_height
                ) && $write_image($new_img, $new_file_path, $image_quality);
        // Free up memory (imagedestroy does not delete files):
        @imagedestroy($src_img);
        @imagedestroy($new_img);
        return $success;
    }