Java：使用 Graphics2D 类来绘制图像

过程介绍

创建一个 BufferedImage 对象

• 首先创建一个 BufferedImage 对象来表示图像

创建一个 Graphics2D 对象

• 然后使用 createGraphics() 方法创建一个 Graphics2D 对象

绘制字符和干扰线

• 最后通过该对象绘制字符和干扰线。

将生成的图像保存到文件

• 使用 ImageIO.write() 方法将生成的图像保存到文件中，或者将其输出到控制台。

示例代码

import java.awt.*;  
import java.awt.image.BufferedImage;  
import java.util.Random;

public class CaptchaGenerator {

    private static final String CHAR_POOL = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789";  
    private static final int WIDTH = 160;  
    private static final int HEIGHT = 50;  
    private static final int CHAR_NUM = 4;  
    private static final int LINE_NUM = 10;

    public static void main(String[] args) {  
        BufferedImage captchaImage = generateCaptchaImage();  
        // 保存图片到文件  
        // ImageIO.write(captchaImage, "png", new File("captcha.png"));  
        // 输出图片到控制台  
        ImageIO.write(captchaImage, "png", System.out);  
    }

    private static BufferedImage generateCaptchaImage() {  
        BufferedImage image = new BufferedImage(WIDTH, HEIGHT, BufferedImage.TYPE_INT_RGB);  
        Graphics2D g = image.createGraphics();  
        Random random = new Random();

        // 设置背景颜色  
        g.setColor(Color.WHITE);  
        g.fillRect(0, 0, WIDTH, HEIGHT);

        // 绘制字符  
        for (int i = 0; i < CHAR_NUM; i++) {  
            g.setColor(getRandomColor());  
            char c = getRandomChar();  
            g.drawString(String.valueOf(c), 30 * i + 20, 30);  
        }

        // 绘制干扰线  
        for (int i = 0; i < LINE_NUM; i++) {  
            g.setColor(getRandomColor());  
            int x1 = random.nextInt(WIDTH);  
            int y1 = random.nextInt(HEIGHT);  
            int x2 = random.nextInt(WIDTH);  
            int y2 = random.nextInt(HEIGHT);  
            g.drawLine(x1, y1, x2, y2);  
        }

        g.dispose();  
        return image;  
    }

    private static Color getRandomColor() {  
        Random random = new Random();  
        int r = random.nextInt(256);  
        int g = random.nextInt(256);  
        int b = random.nextInt(256);  
        return new Color(r, g, b);  
    }

    private static char getRandomChar() {  
        Random random = new Random();  
        int index = random.nextInt(CHAR_POOL.length());  
        return CHAR_POOL.charAt(index);  
    }  
}