/**
 * 裁剪 + 缩放图片
 * @param array $params 包含x,y,width,height,path
 * @return string
 */
public function tailer_image($params){
    //$target_width,$target_height是缩放图片的大小
    $target_width = 256;
    $target_height = 256;
    $source_x = intval($params['x']);
    $source_y = intval($params['y']);
    $cropped_width = intval($params['width']);
    $cropped_height = intval($params['height']);
    $source_path = trim($params['path']);
    $path = 'files/uploads/images/';
    list($source_width,$source_height) = getimagesize($source_path);
    //获取图片的扩展名
    $extend_name = ltrim(strrchr(strtolower($source_path),'.'),'.');
    if(!in_array($extend_name,array('jpg','jpeg','png'))){
        return array(
                    array('message'=>"图片扩展名不正确，只允许'jpg','jpeg','png'"),
                    400
                );
    }
 
    switch ($extend_name) {
        case 'jpg':
            $source_image = imagecreatefromjpeg($source_path);
            break;
        case 'jpeg':
            $source_image = imagecreatefromjpeg($source_path);
            break;
        case 'png':
            $source_image = imagecreatefrompng($source_path);
            break;
    }
     
    $target_image  = imagecreatetruecolor($target_width, $target_height);
    $cropped_image = imagecreatetruecolor($cropped_width, $cropped_height);
    // 裁剪
    imagecopy($cropped_image, $source_image, 0, 0, $source_x, $source_y, $cropped_width, $cropped_height);
    // 缩放
    imagecopyresampled($target_image, $cropped_image, 0, 0, 0, 0, $target_width, $target_height, $cropped_width, $cropped_height);
    $filename = md5(microtime()).'.'.$extend_name;
    $dst_url = $path.$filename;
    //输出图像到$dst_url文件
    imagejpeg($target_image, $dst_url);
    return $dst_url;
}