simplecaptcha.java

基于Java平台的、功能强大的验证码图片生成工具

package nl.captcha.servlet;
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.Servlet;
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;

/**
 * @version 	0.1
 * @author		[e-mail]
 */
public class SimpleCaptcha extends HttpServlet implements Servlet {

	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' };

	/**
	* @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 = 70;

		int car = captchars.length - 1;

		String test = "";
		for (int i = 0; i < 6; i++) {
			test += captchars[generator.nextInt(car) + 1];
		}
		// this key can be read from any controller to check wether user
		// is a computer or human..
		req.getSession().setAttribute(SimpleCaptcha.SIMPLE_CAPCHA_SESSION_KEY, test);

		JPEGImageEncoder encoder =
			JPEGCodec.createJPEGEncoder(resp.getOutputStream());

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

		Graphics2D graphics = bi.createGraphics();
		graphics.setBackground(Color.gray);
		graphics.setColor(Color.gray);
		
		graphics.fillRect(0, 0, bi.getWidth(), bi.getHeight());
	  
		//graphics.drawLine( 0, generator.nextInt(ImageHeight)+1, ImageWidth, generator.nextInt(ImageHeight)+1);

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

		//graphics.drawString(attstr.getIterator(), 0, 50);

		//Font font = new Font()

		TextLayout textTl =
			new TextLayout(
				test,
				new Font("Courier", Font.BOLD, 70),
				new FontRenderContext(null, true, false));
		AffineTransform textAt = graphics.getTransform();

		textTl.draw(graphics, 4, 60);
		int w = bi.getWidth();
		int h = bi.getHeight();
		shear(graphics, w, h, Color.gray);
		this.drawThickLine(
			graphics,
			0,
			generator.nextInt(ImageHeight) + 1,
			ImageWidth,
			generator.nextInt(ImageHeight) + 1,
			4,
			Color.red);



		

		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(10) + 5;

		boolean borderGap = true;
		int frames = 15;
		int phase = generator.nextInt(5) + 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(30) + 10; // 50;

		boolean borderGap = true;
		int frames = 15;
		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);
	}

}