使用Java代码生成一张图片中使用到的类有：BufferedImage，Graphics，ImageIO；

example：绘制一张图片，背景为白色，字体为蓝色，内容为“hello image”的图片

编写步骤如下：

public class DrawImage {
    @Test
    public void drawImage() throws FileNotFoundException, IOException {
        // 获取图片的缓冲区，也就是所谓的画布
        BufferedImage bufferedImage = new BufferedImage(80, 35, BufferedImage.TYPE_INT_RGB);
        //获取画笔，画笔用于在画布上进行绘制
        Graphics paint = bufferedImage.getGraphics();
        //设置画笔的颜色
        paint.setColor(Color.WHITE);
        //绘制画布的背景色
        paint.fillRect(0, 0, 80, 35);
        //设置画笔的颜色
        paint.setColor(Color.blue);
        //绘制显示的具体内容
        paint.drawString("hello image",5,20);
        //绘制完成保存文件
        ImageIO.write(bufferedImage, "jpeg", new FileOutputStream("/Users/wujinli/Desktop/java-draw.jpg"));
这样可以生成一张带有hello image字样的图片了；
在实际开发中，我们在登陆或者注册页面会涉及到图形验证码的场景，线收集一个生成图片验证码的工具类：
import java.awt.BasicStroke;
import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics2D;
import java.awt.image.BufferedImage;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.OutputStream;
import java.util.Random;
import javax.imageio.ImageIO;
public class VerifyCode {
    private int w = 70;
    private int h = 35;
    private Random r = new Random();
    // 定义有那些字体
    private String[] fontNames = { "宋体", "华文楷体", "黑体", "微软雅黑", "楷体_GB2312" };
    // 定义有那些验证码的随机字符
    private String codes = "23456789abcdefghjkmnopqrstuvwxyzABCDEFGHJKLMNOPQRSTUVWXYZ";
    // 生成背景色
    private Color bgColor = new Color(250, 250, 250);
    // 用于gettext 方法 获得生成的验证码文本
    private String text;
    // 生成随机颜色
    private Color randomColor() {
        int red = r.nextInt(150);
        int green = r.nextInt(150);
        int blue = r.nextInt(150);
        return new Color(red, green, blue);
    // 生成随机字体
    private Font randomFont() {
        int index = r.nextInt(fontNames.length);
        String fontName = fontNames[index];
        int style = r.nextInt(4);
        int size = r.nextInt(5) + 24;
        return new Font(fontName, style, size);
    // 画干扰线
    private void drawLine(BufferedImage image) {
        int num = 3;
        Graphics2D g2 = (Graphics2D) image.getGraphics();
        for (int i = 0; i < num; i++) {
            int x1 = r.nextInt(w);
            int y1 = r.nextInt(h);
            int x2 = r.nextInt(w);
            int y2 = r.nextInt(h);
            g2.setStroke(new BasicStroke(1.5F));// 不知道
            g2.setColor(Color.blue);
            g2.drawLine(x1, y1, x2, y2);
    // 得到codes的长度内的随机数 并使用charAt 取得随机数位置上的codes中的字符
    private char randomChar() {
        int index = r.nextInt(codes.length());
        return codes.charAt(index);
    // 创建一张验证码的图片
    public BufferedImage createImage() {
        BufferedImage image = new BufferedImage(w, h,
                BufferedImage.TYPE_INT_RGB);
        Graphics2D g2 = (Graphics2D) image.getGraphics();
        StringBuilder sb = new StringBuilder();
        // 向图中画四个字符
        for (int i = 0; i < 4; i++) {
            String s = randomChar() + "";
            sb.append(s);
            float x = i * 1.0F * w / 4;
            g2.setFont(randomFont());
            g2.setColor(randomColor());
            g2.drawString(s, x, h - 5);
        this.text = sb.toString();
        drawLine(image);
        // 返回图片
        return image;
    // 得到验证码的文本 后面是用来和用户输入的验证码 检测用
    public String getText() {
        return text;
    // 定义输出的对象和输出的方向
    public static void output(BufferedImage bi, OutputStream fos)
            throws FileNotFoundException, IOException {
        ImageIO.write(bi, "JPEG", fos);
java测试代码：
public class test {
    public static void main(String[] args) throws IOException {
        VerifyCode code = new VerifyCode();
        BufferedImage image = code.createImage();
        ImageIO.write(image,"jpg",new File("/Users/wujinli/Desktop/java-draw.jpg"));
在servlet中可以实现生成图片的功能
public class VerifyCodeServlet extends HttpServlet {
    @Override
    protected void service(HttpServletRequest request, HttpServletResponse response)
            throws ServletException, IOException {
        VerifyCode code = new VerifyCode();
        BufferedImage image = code.createImage();
        ImageIO.write(image,"jpg",response.getOutputStream());
图片的显示可以在html或者jsp文件的实现方式
<img src="/项目名称/VerifyCodeServlet">
现在我们实现了在页面上展示校验码图片，但是在实际开发中呢，我们有再换一张的需求；所以需要动态的去请求验证码展示的图片，则实现过程如下：
<img id="imageverify"
                src="/firstweb/VerifyCodeServlet"> <a
                href="javascript:_changeImage()">换一张</a>
<script type="text/javascript">
    function _changeImage() {
        1.获取图片元素
        2.设置资源
        var imageverify = document.getElementById("imageverify");