[PHP知识库]PHP保存图片并且修改图片分辨率（DPI)

   header("Content-type:text/html;charset=utf-8");
   1.引入imagick.php这个文件到项目中，这个文件可以去网上下载
        require_once("../extend/imagick/imagick.php");
        try{
            $this->validate->rule([
              一些参数验证
            ]);
            if(!$this->validate->check($this->params)){
                //打印错误规则，并返回页面
                return json(['code' => 500, 'msg' => $this->validate->getError()]);
            }
            if($this->params['photo_url']!=''){
                $new_file = 保存到服务器的图片路径;
   2.保存不带image头信息的base64格式图片
                $result=file_put_contents($new_file, base64_decode($this->params['photo_url']));
   3.修改图片的分辨率，不传值默认给300                
                $dpi=isset($this->params['dpi'])?$this->params['dpi']:300;
                if($dpi!=0){          
                    $image = new \Imagick();
                    $image->readImage($new_file);
                    $image->setImageResolution($dpi,$dpi);
                    $image->resampleImage($dpi,$dpi,\imagick::FILTER_UNDEFINED,0);
                    $image->writeImage($new_file);
                }
                if (!$result) throw new \Exception('图片存储失败');
            }