ThinkPHP5 は画像のサムネイルを動的に生成します

<IfModule mod_rewrite.c>
  Options +FollowSymlinks -Multiviews
  RewriteEngine On
 
  RewriteCond %{REQUEST_FILENAME} !-d
  RewriteCond %{REQUEST_FILENAME} !-f
  RewriteRule ^public/upload/(.*)/(.*)/(.*)_(\d+)_(\d+).(png|jpg|jpeg|gif)$ /index.php/api/Attachment/thumbnail/module/$1/date/$2/original/$3/width/$4/height/$5/ext/$6 [L,R]
 
  RewriteCond %{REQUEST_FILENAME} !-d
  RewriteCond %{REQUEST_FILENAME} !-f
  RewriteRule ^(.*)$ index.php/$1 [QSA,PT,L]
</IfModule>

public function thumbnail() {
        $savePath = Config::get('attachment_path');
        $defaultImage = $savePath.'default.jpg';
        $params = Request::instance()->param();
        $module = $params['module'];  // 图片所属模块
        $date = $params['date'];      // 图片上传日期
        $original = $params['original']; // 原始图片名称（不含后缀）
        $width = $params['width'];    // 目标图片宽度
        $height = $params['height'];  // 目标图片高度
        $ext = $params['ext'];        // 图片后缀
        $originName = sprintf('%s%s/%s/%s.%s',$savePath,$module,$date,$original,$ext);
        $targetName = sprintf('%s%s/%s/%s_%s_%s.%s',$savePath,$module,$date,$original,$width,$height,$ext);
        if (!file_exists($originName)) {
            $originName = $defaultImage;
            $targetName = sprintf('%sdefault_%s_%s.jpg',$savePath,$width,$height);
        }
        $image = Image::open($originName);
        $thumb = $image->thumb($width, $height);
        if (!file_exists($targetName)) {
            $thumb->save($targetName);
        }
        $thumb->preview();
    }

/**
     * 预览图像
     * @param int         $quality   图像质量
     * @param bool        $interlace 是否对JPEG类型图像设置隔行扫描
     * @return $this
     */
    public function preview($quality = 100, $interlace = true)
    {
        $type = $this->info['type'];
        header('content-type:'.$this->info['mime']);
        if ('jpeg' == $type || 'jpg' == $type) {
            //JPEG图像设置隔行扫描
            imageinterlace($this->im, $interlace);
            imagejpeg($this->im, null, $quality);
        } elseif ('gif' == $type && !empty($this->gif)) {
            imagegif($this->im, null);
        } elseif ('png' == $type) {
            //设定保存完整的 alpha 通道信息
            imagesavealpha($this->im, true);
            //ImagePNG生成图像的质量范围从0到9的
            imagepng($this->im, null, min((int) ($quality / 10), 9));
        } else {
            $fun = 'image' . $type;
            $fun($this->im, '');
        }
       exit;
    }