Android 获取随机验证码功能示例

 package cn.hk.image; 
import java.awt.BasicStroke; 
import java.awt.Color; 
import java.awt.Font; 
import java.awt.Graphics2D; 
import java.awt.image.BufferedImage; 
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(); 
  // {"宋体", "华文楷体", "黑体", "华文新魏", "华文隶书", "微软雅黑", "楷体_GB2312"} 
  private String[] fontNames = {"宋体", "华文楷体", "黑体", "微软雅黑", "楷体_GB2312"}; 
  // 可选字符 
  private String codes = "23456789abcdefghjkmnopqrstuvwxyzABCDEFGHJKMNPQRSTUVWXYZ"; 
  // 背景色 
  private Color bgColor = new Color(255, 255, 255); 
  // 验证码上的文本 
  private String text ; 
  // 生成随机的颜色 
  private Color randomColor () { 
    int red = r.nextInt(150); 
    int green = r.nextInt(150); 
    int blue = r.nextInt(150); 
    return new Color(red, green, blue); 
  } 
  // 生成随机的字体 
  private Font randomFont () { 
    int index = r.nextInt(fontNames.length); 
    String fontName = fontNames[index];//生成随机的字体名称 
    int style = r.nextInt(4);//生成随机的样式, 0(无样式), 1(粗体), 2(斜体), 3(粗体+斜体) 
    int size = r.nextInt(5) + 24; //生成随机字号, 24 ~ 28 
    return new Font(fontName, style, size); 
  } 
  // 画干扰线 
  private void drawLine (BufferedImage image) { 
    int num = 3;//一共画3条 
    Graphics2D g2 = (Graphics2D)image.getGraphics(); 
    for(int i = 0; i < num; i++) {//生成两个点的坐标，即4个值 
      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));  
      g2.setColor(Color.BLUE); //干扰线是蓝色 
      g2.drawLine(x1, y1, x2, y2);//画线 
    } 
  } 
  // 随机生成一个字符 
  private char randomChar () { 
    int index = r.nextInt(codes.length()); 
    return codes.charAt(index); 
  } 
  // 创建BufferedImage，图片缓存区 
  private BufferedImage createImage () { 
    BufferedImage image = new BufferedImage(w, h, BufferedImage.TYPE_INT_RGB);  
    Graphics2D g2 = (Graphics2D)image.getGraphics();  
    g2.setColor(this.bgColor); 
    g2.fillRect(0, 0, w, h); 
    return image; 
  } 
  // 调用这个方法得到验证码 
  public BufferedImage getImage () { 
    BufferedImage image = createImage();//创建图片缓冲区  
    Graphics2D g2 = (Graphics2D)image.getGraphics();//得到绘制环境 
    StringBuilder sb = new StringBuilder();//用来装载生成的验证码文本 
    // 向图片中画4个字符 
    for(int i = 0; i < 4; i++) {//循环四次，每次生成一个字符 
      String s = randomChar() + "";//随机生成一个字母  
      sb.append(s); //把字母添加到sb中 
      float x = i * 1.0F * w / 4; //设置当前字符的x轴坐标 
      g2.setFont(randomFont()); //设置随机字体 
      g2.setColor(randomColor()); //设置随机颜色 
      g2.drawString(s, x, h-5); //画图 
    } 
    this.text = sb.toString(); //把生成的字符串赋给了this.text 
    drawLine(image); //添加干扰线 
    return image;     
  } 
  // 返回验证码图片上的文本 
  public String getText () { 
    return text; 
  } 
  // 保存图片到指定的输出流 
  public static void output (BufferedImage image, OutputStream out)  
        throws IOException { 
    ImageIO.write(image, "JPEG", out); 
  } 
}