code: public static byte[] encode2ByteArray(int width, int high, String verifyCode) throws IOException {
          width = width < 1 ? defaultWidth : width;
          high = high < 1 ? defaultHigh : high;
          ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream();
          outputImage(width, high, byteArrayOutputStream, verifyCode);
          return byteArrayOutputStream.toByteArray();
      }
docs: 得到验证码byte array
  @param width
  @param high
  @param verifyCode
  @return
  @throws IOException