code: public static void encode2ImgFile(int width, int high, String imgFilename, String verifyCode) throws IOException{
          width = width < 1 ? defaultWidth : width;
          high = high < 1 ? defaultHigh : high;
          File outputFile = new File(imgFilename);
          File dir = outputFile.getParentFile();
          if(!dir.exists()){
              dir.mkdirs();
          }
          outputFile.createNewFile();
          FileOutputStream fos = new FileOutputStream(outputFile);
          outputImage(width, high, fos, verifyCode);
          fos.close();
      }
docs: 生成验证码文件
  @param width
  @param high
  @param imgFilename
  @param verifyCode
  @throws IOException