稳妥第一步：图片转base64(字符串)

// 返回Base64编码过的字节数组字符串  

       

 String imgData = null;
		byte[] data = null; 
		try {

                        //本机服务器资源

			data = FileUtil.getFileBytes((String)("URL"));
	        // 对字节数组Base64编码  
	        imgData = new BASE64Encoder().encode(data);
	    }catch (Exception e) {  
	        e.printStackTrace();  
	    } 

//user头像数据:url是一个链接地址时的转化

String imgData = null;
		byte[] data = null;
		try {
			URL url = new URL(cupService.getHeadimgByOpenId(openid));
			HttpURLConnection conn = (HttpURLConnection) url.openConnection();
			conn.setRequestMethod("GET");
			conn.setConnectTimeout(5 * 1000);
			InputStream inStream = conn.getInputStream();
			data = new byte[inStream.available()];
			inStream.read(data);
			inStream.close();
			imgData = new Base64Encoder().encode(data);
		} catch (Exception e) {
			e.printStackTrace();
		}