图片验证码常用方法

• 获得随机颜色

private static Color getRandomColor() {  
        return new Color(random.nextInt(255), random.nextInt(255),random.nextInt(255));  
    } 

• 获得颜色的反色

private static Color getReverseColor(Color c) {  
        return new Color(255 - c.getRed(), 255 - c.getGreen(),255 - c.getBlue());  
    } 

• 绘制噪音点

private static void drawNoisePoint(int width, int height, int num,Graphics2D g) {  
        for (int i = 0, n = random.nextInt(num); i < n; i++) {// 绘制最多num个噪音点  
            g.drawRect(random.nextInt(width), random.nextInt(height), 1, 1);// 随机噪音点  
        }  
    }

• 绘制干扰线

 private static void drawInterferingLine(int width, int height, int n,Graphics2D g) {  
        for (int i = 0; i < n; i++) {  
            int x = random.nextInt(width - 1);  
            int y = random.nextInt(height - 1);  
            int xl = random.nextInt(6) + 1;  
            int yl = random.nextInt(12) + 1;  
            g.drawLine(x, y, x + xl + 40, y + yl + 20);  
        }  
    }  

• 扭曲图片

private static void shear(int width, int height, Graphics2D g, Color color) {  
        shearX(g, width, height, color);  
        shearY(g, width, height, color);  
    } 

• 沿Y轴扭曲

private static void shearY(Graphics2D g, int width, int height, Color color) {  
        int period = random.nextInt(40) + 10; // 周期  
        int frames = 20; // 帧  
        int phase = 7; // 相位  
        for (int i = 0; i < width; i++) {  
            double d = (double) (period >> 1)* Math.sin((double) i / (double) period + (Math.PI * 2 * (double) phase) / (double) frames);  
            g.copyArea(i, 0, 1, height, 0, (int) d);  
            g.setColor(color);  
            g.drawLine(i, (int) d, i, 0);  
            g.drawLine(i, (int) d + height, i, height);  
        }  
    }  

• 沿X轴扭曲

private static void shearX(Graphics2D g, int width, int height, Color color) {  
        int period = random.nextInt(2);  
        int frames = 1;  
        int phase = random.nextInt(2);  
        for (int i = 0; i < height; i++) {  
            double d = (double) (period >> 1)* Math.sin((double) i / (double) period + (Math.PI * 2 * (double) phase) / (double) frames);  
            g.copyArea(0, i, width, 1, (int) d, 0);  
            g.setColor(color);  
            g.drawLine((int) d, i, 0, i);  
            g.drawLine((int) d + width, i, width, i);  
        }  
    }  

• 创建验证码图片

public static void outputImage(int width, int height, OutputStream os,String randomString) throws IOException {  
        int verifySize = randomString.length(); // 验证码长度  
        Color color = getRandomColor();// 随机颜色，用于背景色  
        Color reverse = getReverseColor(color);// 反色，用于前景色  
  
        BufferedImage bi = new BufferedImage(width, height,BufferedImage.TYPE_INT_RGB);// 创建一个彩色图片  
  
        Graphics2D g = bi.createGraphics();// 获取绘图对象  
  
        g.setRenderingHint(RenderingHints.KEY_ANTIALIASING,RenderingHints.VALUE_ANTIALIAS_ON); // 设置图像抗锯齿  
        g.setFont(new Font(Font.SANS_SERIF, Font.ITALIC, height - 4));// 设置字体: Serif的意思是，在字的笔划开始及结束的地方有额外的装饰，而且笔划的粗细会因直横的不同而有不同。相反的，Sans Serif则没有这些额外的装饰，笔划粗细大致差不多  
        g.setColor(color);// 设置颜色  
        g.fillRect(0, 0, width, height);// 绘制背景:用这个颜色填充这个区域  
        g.setColor(reverse);// 设置颜色  
  
        for (int i = 0; i < verifySize; i++) { // 绘制验证码  
            g.drawChars(randomString.toCharArray(), i, 1,((width - 10) / verifySize) * i + 5, height / 2 + height/ 2 - 10);  
        }  
  
        drawNoisePoint(width, height, 500, g); // 绘制最多1000个噪音点  
  
        drawInterferingLine(width, height, 30, g); // 产生30条干扰线  
  
        shear(width, height, g, color);// 使图片扭曲  
  
        g.dispose();// 释放由此 Window、其子组件及其拥有的所有子组件所使用的所有本机屏幕资源  
  
        ImageIO.write(bi, "jpg", os);  
    }  

• 生成指定验证码图片文件

public static void outputImageFile(int width, int height, File file,String code) throws IOException {  
        if (file == null) {  
            return;  
        }  
        File dir = file.getParentFile();// 获得父目录  
        if (!dir.exists()) { // 如果父目录不存在，则创建一个  
            dir.mkdirs();  
        }  
        try {  
            file.createNewFile();  
            FileOutputStream fos = new FileOutputStream(file);  
            outputImage(width, height, fos, code); // 创建验证码图片  
            fos.close(); // 关闭流  
        } catch (IOException e) {  
            throw e;  
        }  
    }  

转自：http://blog.csdn.net/paulangsky/article/details/52191696