java輸出扭曲驗證碼 (效果很好)

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' }; 

/** 
  * 產生隨機字體 
  * 
  * @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)]; 
} 

/** 
  * 隨機產生定義的顏色 
  * 
  * @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; 
  /** 
   * 產生隨機字符串 
   */ 
  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); 
  /** 
   * 得到輸出流 
   */ 
  JPEGImageEncoder encoder = JPEGCodec.createJPEGEncoder(resp 
    .getOutputStream()); 

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

  Graphics2D graphics = bi.createGraphics(); 

  /** 
   * 設置背景色 
   */ 
  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); 
} 

}