问COS 预签名url上传图片，图片无法预览，下载的图片也无法预览？

        key = keyPrefix.get(fileType) + "/" + fileName + new Date().getTime() + fileFormat;
        //设置签名过期时间为30分钟
        Date expirationDate = new Date(System.currentTimeMillis() + 30 * 60 * 1000);

        HttpMethodName method;
        if (urlType == FileUrlType.UPLOAD.getTemp()){
            method = HttpMethodName.PUT;
        }else {
            method = HttpMethodName.GET;
        }
        URL url = cosClient.generatePresignedUrl(bucketName, key, expirationDate, method);