java输出扭曲验证码

import java.awt.Color;
import java.awt.Font;
import java.awt.Graphics;
import java.awt.Graphics2D;
import java.awt.font.FontRenderContext;
import java.awt.font.TextLayout;
import java.awt.geom.AffineTransform;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.text.AttributedString;
import java.util.Random;

import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import com.sun.image.codec.jpeg.JPEGCodec;
import com.sun.image.codec.jpeg.JPEGImageEncoder;



public class SimpleCaptcha extends HttpServlet {
private Random generator = new Random();
private final static String SIMPLE_CAPCHA_SESSION_KEY = "SIMPLE_CAPCHA_SESSION_KEY";

private static char[] captchars = new char[] { 'a', 'b', 'c', 'd', 'e',
   '2', '3', '4', '5', '6', '7', '8', 'g', 'f', 'y', 'n', 'm', 'n',
   'p', 'w', 'x' };

/**
  * 产生随机字体
  *
  * @return
  */
private Font getFont() {
  Random random = new Random();
  Font font[] = new Font[5];
  font[0] = new Font("Ravie", Font.PLAIN, 45);
  font[1] = new Font("Antique Olive Compact", Font.PLAIN, 45);
  font[2] = new Font("Forte", Font.PLAIN, 45);
  font[3] = new Font("Wide Latin", Font.PLAIN, 40);
  font[4] = new Font("Gill Sans Ultra Bold", Font.PLAIN, 45);
  return font[random.nextInt(5)];
}

/**
  * 随机产生定义的颜色
  *
  * @return
  */
private Color getRandColor() {
  Random random = new Random();
  Color color[] = new Color[10];
  color[0] = new Color(32, 158, 25);
  color[1] = new Color(218, 42, 19);
  color[2] = new Color(31, 75, 208);
  return color[random.nextInt(3)];
}

/**
  * @see javax.servlet.http.HttpServlet#void
  *      (javax.servlet.http.HttpServletRequest,
  *      javax.servlet.http.HttpServletResponse)
  */
public void doGet(HttpServletRequest req, HttpServletResponse resp)
   throws ServletException, IOException {

  int ImageWidth = 200;
  int ImageHeight = 100;

  int car = captchars.length - 1;
  /**
   * 产生随机字符串
   */
  String test = "";
  for (int i = 0; i < 4; i++) {
   test += captchars[generator.nextInt(car) + 1];
  }
  /**
   * 放放Session
   */
  req.getSession().setAttribute(SimpleCaptcha.SIMPLE_CAPCHA_SESSION_KEY,
    test);
  /**
   * 得到输出流
   */
  JPEGImageEncoder encoder = JPEGCodec.createJPEGEncoder(resp
    .getOutputStream());

  BufferedImage bi = new BufferedImage(ImageWidth + 10, ImageHeight,
    BufferedImage.TYPE_BYTE_INDEXED);

  Graphics2D graphics = bi.createGraphics();

  /**
   * 设置背景色
   */
  graphics.setColor(Color.white);
 
  graphics.fillRect(0, 0, bi.getWidth(), bi.getHeight());

  graphics.setColor(Color.black);
  AttributedString attstr = new AttributedString(test);

  TextLayout textTl = new TextLayout(test, new Font("Courier", Font.BOLD,
    70), new FontRenderContext(null, true, false));
  AffineTransform textAt = graphics.getTransform();
  graphics.setFont(new Font("Courier", Font.BOLD,70));
  graphics.setColor(this.getRandColor());
  graphics.drawString(test, 10,70);
//  textTl.draw(graphics, 4, 60);
  int w = bi.getWidth();
  int h = bi.getHeight();
  shear(graphics, w, h, Color.white);
  // this.drawThickLine(graphics, 0, generator.nextInt(ImageHeight) + 1,
  // ImageWidth, generator.nextInt(ImageHeight) + 1, 4, Color.BLACK);

  resp.setContentType("image/jpg");

  encoder.encode(bi);

}

private void shear(Graphics g, int w1, int h1, Color color) {

  shearX(g, w1, h1, color);
  shearY(g, w1, h1, color);
}

public void shearX(Graphics g, int w1, int h1, Color color) {

  int period = generator.nextInt(2);

  boolean borderGap = true;
  int frames = 1;
  int phase = generator.nextInt(2);

  for (int i = 0; i < h1; i++) {
   double d = (double) (period >> 1)
     * Math.sin((double) i / (double) period
       + (6.2831853071795862D * (double) phase)
       / (double) frames);
   g.copyArea(0, i, w1, 1, (int) d, 0);
   if (borderGap) {
    g.setColor(color);
    g.drawLine((int) d, i, 0, i);
    g.drawLine((int) d + w1, i, w1, i);
   }
  }

}

public void shearY(Graphics g, int w1, int h1, Color color) {

  int period = generator.nextInt(40) + 10; // 50;

  boolean borderGap = true;
  int frames = 20;
  int phase = 7;
  for (int i = 0; i < w1; i++) {
   double d = (double) (period >> 1)
     * Math.sin((double) i / (double) period
       + (6.2831853071795862D * (double) phase)
       / (double) frames);
   g.copyArea(i, 0, 1, h1, 0, (int) d);
   if (borderGap) {
    g.setColor(color);
    g.drawLine(i, (int) d, i, 0);
    g.drawLine(i, (int) d + h1, i, h1);
   }

  }

}

private void drawThickLine(Graphics g, int x1, int y1, int x2, int y2,
   int thickness, Color c) {

  // The thick line is in fact a filled polygon
  g.setColor(c);
  int dX = x2 - x1;
  int dY = y2 - y1;
  // line length
  double lineLength = Math.sqrt(dX * dX + dY * dY);

  double scale = (double) (thickness) / (2 * lineLength);

  // The x and y increments from an endpoint needed to create a
  // rectangle...
  double ddx = -scale * (double) dY;
  double ddy = scale * (double) dX;
  ddx += (ddx > 0) ? 0.5 : -0.5;
  ddy += (ddy > 0) ? 0.5 : -0.5;
  int dx = (int) ddx;
  int dy = (int) ddy;

  // Now we can compute the corner points...
  int xPoints[] = new int[4];
  int yPoints[] = new int[4];

  xPoints[0] = x1 + dx;
  yPoints[0] = y1 + dy;
  xPoints[1] = x1 - dx;
  yPoints[1] = y1 - dy;
  xPoints[2] = x2 - dx;
  yPoints[2] = y2 - dy;
  xPoints[3] = x2 + dx;
  yPoints[3] = y2 + dy;

  g.fillPolygon(xPoints, yPoints, 4);
}

}