java 实现输出随机图片实例代码
输出随机图片(CAPTCHA图像):Completely Automated Public Turing Test to Tell Computers and Humans Apart (全自动区分计算机和人类的测试)
相关主要类(JDK 查看API)
BufferedImage:内存图像
Graphics：画笔
ImageIO：输出图像
放在html页面上<img src/>
注意：浏览器默认会缓存图片
public static int WIDTH = 120;
public static int HEIGHT = 25;
public void doGet(HttpServletRequest request, HttpServletResponse response)
throws ServletException, IOException {
response.setContentType("text/html");
//创建内存图像
BufferedImage image = new BufferedImage(WIDTH,HEIGHT,BufferedImage.TYPE_INT_RGB);
//勾勒图像
Graphics graphics = image.getGraphics();
//设置背景
graphics.setColor(Color.WHITE);
graphics.fillRect(0, 0, WIDTH, HEIGHT);
//设置边框
graphics.setColor(Color.BLUE);
graphics.drawRect(1, 1, WIDTH-2, HEIGHT-2);
//画干扰线
graphics.setColor(Color.YELLOW);
for(int i=0;i<8;i++){
int xStart = new Random().nextInt(WIDTH);
int yStart = new Random().nextInt(HEIGHT);
int xEnd = new Random().nextInt(WIDTH);
int yEnd = new Random().nextInt(HEIGHT);
graphics.drawLine(xStart, yStart, xEnd, yEnd);
}
//写随机数
graphics.setColor(Color.RED);
int x = 5;
for(int i=0;i<4;i++){
graphics.drawString(new Random().nextInt(9)+"", x, 20);
x+=30;
}
response.setContentType("image/jpeg");//设置响应格式
ImageIO.write(image, "jpeg", response.getOutputStream());
}
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