Java生成图片验证码

目录

• Java生成图片验证码
  • 参考资料
  • 步骤
    • 1.编写图形随机码生成器
    • 2.编写Controller,将生成的图片响应码写到响应流
    • 3.测试

Java生成图片验证码

参考资料

1. Java实现图片验证码
2. Java图片验证码的生成与验证
3. https://docs.oracle.com/javase/tutorial/2d/index.html
4. 多线程下ThreadLocalRandom用法

步骤

1.编写图形随机码生成器

package com.*.util;

import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.image.BufferedImage;
import java.util.HashMap;
import java.util.Map;
import java.util.concurrent.ThreadLocalRandom;

/**
 * 图片验证码生成器
 * 
 * @author limo
 * @date 2022-01-24 17:19:023
 */
public class ImageVerifyCodeGenerator {

    // 随机字符词典(去掉0和1,因为它们和字母O,l在图片展示容易混淆)
    public static final String RANDOM_CHARS = "23456789ABCDEFGHIJKLMNOPQRSTUVWXYZ";
    // 字体数组
    public static final String[] FONT_NAMES = { "Chandas" };

    /**
     * 生成4位随机图片验证码
     * 
     * @return
     */
    public static synchronized Map<String, Object> generate() {

	// 1. 初始化图片缓冲器
	BufferedImage image = initImage();
	// 2. 生成随机验证码
	String[] codes = createVerifyCodes();
	// 3. 验证码写入图片中
	draw(image, codes);
	// 4. 返回图片和验证码
	Map<String, Object> imageInfo = new HashMap<String, Object>();
	imageInfo.put("image", image);
	StringBuffer verfyCode = new StringBuffer();
	for (String c : codes) {
	    verfyCode.append(c);
	}
	imageInfo.put("code", verfyCode.toString());
	return imageInfo;
    }

    /**
     * 生成图片验证码
     * 
     * @param width           图片验证码宽度
     * @param height          图片验证码高度
     * @param verfyCodeNumber 验证码字符个数
     * @return 图片验证码和验证码
     */
    public static synchronized Map<String, Object> generate(int width, int height, int verfyCodeNumber) {

	// 1. 初始化图片缓冲器
	BufferedImage image = initImage(100, 40, BufferedImage.TYPE_INT_RGB);
	// 2. 生成随机验证码
	String[] codes = createVerifyCodes(verfyCodeNumber);
	// 3. 验证码写入图片中
	draw(image, codes);
	// 4. 返回图片和验证码
	Map<String, Object> imageInfo = new HashMap<String, Object>();
	imageInfo.put("image", image);
	StringBuffer verfyCode = new StringBuffer();
	for (String c : codes) {
	    verfyCode.append(c);
	}
	imageInfo.put("code", verfyCode);
	return imageInfo;
    }

    public static BufferedImage initImage() {
	// 默认图片宽100,高 40 底色白色,颜色系统使用RGB
	return initImage(100, 40, BufferedImage.TYPE_INT_RGB);
    }

    public static BufferedImage initImage(int width, int height, int imageType) {
	BufferedImage image = initImage(width, height, imageType, Color.white);
	return image;
    }

    public static BufferedImage initImage(int width, int height, int imageType, Color color) {
	BufferedImage image = new BufferedImage(width, height, imageType);
	// 获取画笔
	Graphics graphics = image.getGraphics();
	// 设置底色
	graphics.setColor(color);
	// 画一个长方形
	graphics.fillRect(0, 0, width, height);
	return image;
    }

    public static synchronized String[] createVerifyCodes() {
	return createVerifyCodes(4);
    }

    public static String[] createVerifyCodes(int verfyCodeNumber) {
	return createVerifyCodes(RANDOM_CHARS.toCharArray(), verfyCodeNumber);
    }

    public static String[] createVerifyCodes(char[] chars, int verfyCodeNumber) {
	String[] codes = new String[verfyCodeNumber];
	for (int i = 0; i < codes.length; i++) {
	    char c = randomChar(chars);
	    codes[i] = String.valueOf(c);
	}
	return codes;
    }

    /**
     * 获取随机字符
     *
     * @return
     */
    public static synchronized char randomChar(char[] chars) {
	int index = ThreadLocalRandom.current().nextInt(chars.length);
	return RANDOM_CHARS.charAt(index);
    }

    public static void draw(BufferedImage image, String[] codes) {
	int width = image.getWidth();
	int height = image.getHeight();
	Graphics2D graphics = (Graphics2D) image.getGraphics();
	for (int i = 0; i < codes.length; i++) {
	    // 计算字符所在图片中x的位置,一般按字符个数平均分
	    float x = i * 1.0f * width / codes.length;
	    float y = height - 5 / 1.0f;
	    drawString(graphics, codes[i], x, y);
	}
	graphics.dispose();
    }

    public static void drawString(Graphics2D graphics, String code, float x, float y) {
	drawString(graphics, code, x, y, randomFont(), randomColor());
    }

    public static void drawString(Graphics2D graphics, String code, float x, float y, Font font, Color color) {
	graphics.setColor(color);
	graphics.setFont(font);
	graphics.drawString(code, x, y);
    }

    /**
     * 获取随机字体
     *
     * @return
     */
    public static Font randomFont() {
	return randomFont(FONT_NAMES);
    }

    /**
     * 获取随机字体
     *
     * @return
     */
    public static Font randomFont(String[] fonts) {
	int index = ThreadLocalRandom.current().nextInt(fonts.length); // 获取随机的字体
	String fontName = fonts[index];
	int style = ThreadLocalRandom.current().nextInt(4); // 随机获取字体的样式，0是无样式，1是加粗，2是斜体，3是加粗加斜体
	int size = ThreadLocalRandom.current().nextInt(10) + 24; // 随机获取字体的大小
	return new Font(fontName, style, size); // 返回一个随机的字体
    }

    /**
     * 随机颜色
     * 
     * @return
     */
    public static Color randomColor() {
	int r = ThreadLocalRandom.current().nextInt(225); // 这里为什么是225，因为当r，g，b都为255时，即为白色，为了好辨认，需要颜色深一点。
	int g = ThreadLocalRandom.current().nextInt(225);
	int b = ThreadLocalRandom.current().nextInt(225);
	return new Color(r, g, b); // 返回一个随机颜色
    }
}

获取本机可用字体名(按需使用):

   GraphicsEnvironment graphicsEnv =  GraphicsEnvironment.getLocalGraphicsEnvironment();
   String[] fontNames = graphicsEnv.getAvailableFontFamilyNames();

2.编写Controller,将生成的图片响应码写到响应流

    @GetMapping("/verify/code")
    public void verifyCode(HttpServletRequest request, HttpServletResponse response) throws IOException {
	// 生成验证码图片
	Map<String, Object> imageVerifyCode = ImageVerifyCodeGenerator.generate();
	BufferedImage bfm = (BufferedImage) imageVerifyCode.get("image");
	String code = String.valueOf(imageVerifyCode.get("code"));
	System.out.println("验证码:" + code);
	HttpSession session = request.getSession();
	session.setAttribute("verifyCode", code);
    // 使用 ImageIO工具类将 图片验证码输出到响应流
	ImageIO.write(bfm, "PNG", response.getOutputStream());
    }

3.测试

启动应用后,使用 postman 工具请求 http://localhost:8100/verify/code 结果如下:

编写完成.