输出随机认证图片

<!---首先需要用到BufferedImage在内存中构建一张图片----->

BufferedImage img = new BufferedImage(WIDTH, HEIGHT, BufferedImage.TYPE_INT_RGB);

 

<!-----最后一个参数表示一个图像，它具有合成整数像素的 8 位 RGB 颜色分量----->

 

<!---往图片上写需要用到Graphics，相当于一个画笔----->

Graphics g = img.getGraphics();

 

<!---------------新建这4个方法来画---------------------->

setBacoground(g); /*画背景图*/  setBorder(g);/*画边框*/  

setInterferingline(g); /*画干扰线*/  setWord((Graphics2D)g); /*写字,字体旋转需要用到Graphics2D中的rotate方法*/

 

<!-----------告诉浏览器以图片形式打开,将图片写给浏览器------------->

response.setContentType("image/jpeg"); 

ImageIO.write(img, "jpg", response.getOutputStream()); 

<!-----------下面是4个方法的代码------------->

private void setBacoground(Graphics g) {
     g.setColor(Color.WHITE);
     g.fillRect(0, 0, WIDTH, HEIGHT);
}

private void setBorder(Graphics g) {
    g.setColor(Color.black);
    g.drawRect(1, 1, WIDTH-2, HEIGHT-2);

}

private void setInterferingline(Graphics g) {
    g.setColor(Color.red);
    for(int i=0; i<4; i++) {
       int x1 = new Random().nextInt(WIDTH);
       int y1 = new Random().nextInt(HEIGHT);
       int x2 = new Random().nextInt(WIDTH);
      int y2 = new Random().nextInt(HEIGHT);
      g.drawLine(x1, y1, x2, y2);
   }
}

private void setWord(Graphics2D g) {
   g.setColor(Color.BLACK);
   g.setFont(new Font("黑体", Font.BOLD, 20));
   String bute = "这里是常用字的正则表达式，太多就不贴了";
   int x = 5;
   for(int i=0; i<4; i++) {
     int degree = new Random().nextInt() % 30;
     String ch = bute.charAt(new Random().nextInt(bute.length()))+"";
     g.rotate(degree*Math.PI/180,x,20);
     g.drawString(ch,x,20);
     g.rotate(-degree*Math.PI/180,x,25);
     x += 30;
  }
}