public class validateCode{

  private static Random rand = new Random();

  public static void main(String[] args){
    int val1 = rand.nextInt(9);
    int val2 = rand.nextInt(9);
    int val3 = rand.nextInt(9);
    int val4 = rand.nextInt(9);
    String val = val1 + " " + val2 + " " + val3 + " " + val4'
    BufferedImage buf = drawImage(val);
    //將最終的圖片保存到D：//cheng.png下
    ImageIO.write(buf,"png",new File("D://cheng.png");
  }

  public static BufferedImage drawImage(String code){
    int height = 30;
    int width = 60;
    BufferedImage buf = new BufferedImage(width,height,BufferedImage.TYPE_INT_RGB);
    Graphics2D gs = buf.createGraphics();
    gs.setBackground(Color.black);
    gs.drawRect(0,0,width,height); 

    //繪制隨機干擾線
    int total = 100;
    drawRandLine(gs,total);

    //繪制驗證碼
    Font font = new Font("行楷",Font.BOLD,20);
    gs.setFont(font);
    gs.setColor(getRandColor(155,255));
    gs.drawString(code,5,20);

    return buf;
  }

  public static void drawRandLine(Graphics2D gs,int total){

    for(int i=0; i<total; i++){
      int x1 = rand.nextInt(width);
      int x2 = rand.nextInt(width);
      int y1 = rand.nextInt(height);
      int y2 = rand.nextInt(height);
      //設置隨機顏色
      gs.setColor(getRandColor(0,155));
      gs.drawLine(x1,y1,x2,y2);
    }  
  }

  public static Color getRandColor(int from,int to){

    int r = from + rand.nextInt(to-from);
    int g = from + rand.nextInt(to-from);
    int b = from + rand.nextInt(to-from);
    return new Color(r,g,b);  
  }