java 验证码工具

import javax.imageio.ImageIO;
import java.awt.*;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.io.OutputStream;
import java.util.Random;

public class CaptchaUtils {

    private final static Object lock = new Object();

    /**
     * 图片的宽度。
     */
    private int width = 132;

    /**
     * 图片的高度。
     */
    private int height = 40;
    /**
     * 验证码字符个数
     */
    private int codeCount = 4;
    /**
     * 验证码干扰线数
     */
    private int lineCount = 10;


    private static CaptchaUtils instance;

    static {
        synchronized (lock) {
            if (instance == null) {
                instance = new CaptchaUtils();
            }
        }
    }


    public static CaptchaUtils getInstance() {
        return instance;
    }


    private static final char[] codeSequence = {
             'A', 'B', 'C', 'D', 'E', 'F', 'G',
             'H', 'J', 'K', 'M', 'N', 'P', 'Q', 'R', 'S', 'T',
             'U', 'V', 'W', 'X', 'Y', 'Z',
             '1', '2', '3', '4', '5', '6', '7', '8', '9'};

    public String createCode() {
        Random random = new Random(System.currentTimeMillis());

        StringBuffer buffer = new StringBuffer();

        for (int i = 0; i < codeCount; i++) {
            String strRand = String.valueOf(codeSequence[random.nextInt(codeSequence.length)]);
            buffer.append(strRand);
        }

        return buffer.toString().toLowerCase();
    }


    public void draw(String code, OutputStream sos) {

        BufferedImage bufferedImage = this.drawCode(code);


        try {
            ImageIO.write(bufferedImage, "png", sos);
            sos.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    private BufferedImage drawCode(String code) {
        int x = 0, fontHeight = 0, codeY = 0;
        int red = 0, green = 0, blue = 0;

        // 生成随机数
        Random random = new Random(System.currentTimeMillis());
        //每个字符的宽度
        x = width / codeCount;
        //字体的高度
        fontHeight = height - 8;
        codeY = height;

        // 图像buffer
        BufferedImage buffImg = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);
        Graphics2D g = buffImg.createGraphics();

        // 将图像填充为白色
        g.setColor(Color.WHITE);
        g.fillRect(0, 0, width, height);

        Font font = new Font("Arial", Font.PLAIN, fontHeight);
        g.setFont(font);

        for (int i = 0; i < lineCount; i++) {
            red = random.nextInt(255);
            green = random.nextInt(128) + 127;
            blue = random.nextInt(128) + 127;
            g.setColor(new Color(red, green, blue));

            //初始角度必须大于0
            int angRange = random.nextInt(270) + 30;
            int arcX = random.nextInt(width) - (width >> 4);
            int arcY = random.nextInt(height);
            int arcWidth = random.nextInt(width);
            int arcHeight = random.nextInt(height);
            int arcStartAng = random.nextInt(angRange) + 1;
            int arcAng = random.nextInt(angRange) + 1;

            g.drawArc(arcX, arcY, arcWidth, arcHeight, arcStartAng, arcAng);
        }


        int offsetX = random.nextInt(5) + 5;
        int offsetY = random.nextInt(5) + 10;

        for (int i = 0; i < code.length(); i++) {

            String strRand = code.substring(i, i + 1);
            // 产生随机的颜色值，让输出的每个字符的颜色值都将不同。
            red = random.nextInt(255);
            green = random.nextInt(127);
            blue = random.nextInt(255);
            g.setColor(new Color(red, green, blue));
            //正负波动微调


            double degree = (random.nextInt(20) - 10) * Math.PI / 180;
            int fx = (i * x) + offsetX;
            int fy = codeY - offsetY;
            g.rotate(degree, fx, fy);
            g.drawString(strRand, fx, fy);
            //输出完成旋转回来
            g.rotate(-degree, fx, fy);
        }

        return buffImg;
    }


}