二維碼圖片流轉base64

@RequestMapping(value = "/weChatImage",method = RequestMethod.GET)public Response weChatimage(@RequestParam(required=false) int width,@RequestParam(required=false) int height,@RequestParam(required = false) String redirect, HttpServletResponse response) throws Exception{   String code = java.util.UUID.randomUUID().toString();   String code_url = SystemProperties.getValue("ucenter.out.url")+"/weChat/scanCode?state="+code;   //String code_url = "http://localhost:8080/weChat/scanCode?state="+code;   Map<String,Object> map1 = new HashMap<>();   map1.put("redirect",redirect);   redis.opsForValue().set(code,JSON.toJSONString(map1),7,TimeUnit.DAYS);   if(width == 0){      width = 200;//寬度   }   if(height == 0){      height = 200;//高度   }   Map<EncodeHintType,Object> hints = new HashMap<>();   hints.put(EncodeHintType.CHARACTER_SET, "UTF-8");   //生成矩陣   BitMatrix bitMatrix = new MultiFormatWriter().encode(code_url, BarcodeFormat.QR_CODE, width, height, hints);   //字節數組輸出流   ByteArrayOutputStream imageOut = new ByteArrayOutputStream();   MatrixToImageWriter.writeToStream(bitMatrix, "png", imageOut);   //字節數組輸入流   ByteArrayInputStream imageIn = new ByteArrayInputStream(imageOut.toByteArray());   BufferedImage bImage = ImageIO.read(imageIn);   ByteArrayOutputStream bs =new ByteArrayOutputStream();   ImageIO.write(bImage, "png", bs);   String base64 = "data:image/png;base64,"+Base64.byteArrayToBase64(bs.toByteArray());   Map<String,Object> map = new HashMap<>();   map.put("base64",base64);   map.put("url",code_url);   map.put("code",code);   return Response.newInstance().setStatus(Response.SUCCESS).setBody(map);}