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CalcCaptcha

Posted by JOKe on 8/11/2009 11:35:00 AM in ,
This is the source code for a simple captcha that looks like this :

The servlet is easy customizable so you can easy edit it or write your own.

The Captcha is based on the 100 lines JSP captcha explained here : http://www.jroller.com/mlconnor/entry/simple_captcha_jsp
package com.joke.web.servetls;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;

import com.joke.service.Constants;

import java.awt.Color;
import java.awt.Font;
import java.awt.FontMetrics;
import java.awt.Graphics2D;
import java.awt.RenderingHints;
import java.awt.geom.AffineTransform;
import java.awt.image.BufferedImage;
import java.io.IOException;
import java.util.Iterator;

import javax.imageio.IIOImage;
import javax.imageio.ImageIO;
import javax.imageio.ImageWriteParam;
import javax.imageio.ImageWriter;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

public class CaptchaServlet extends HttpServlet {
/**
* Logger for this class
*/
private static final Log logger = LogFactory.getLog(CaptchaServlet.class);

/**
*
*/
private static final long serialVersionUID = -3425450129222434319L;

/*
* Constants
*/
private static final String SESSION_PARAM_CAPTCHA_IMAGE = Constants.SESSION_PARAM_DEFAULT_CAPTCHA_IMAGE;
private static final String IMAGE_MIME_TYPE_JPG = "image/jpg";
private static final String CAPTCHA_FONT = "Arial";
private static final String REQUEST_PARAM_HEIGHT = "height";
private static final String REQUEST_PARAM_WIDTH = "width";

// private static final int MAX_LINES_TO_DRAW = 6;
// private static final int MIN_LINES_TO_DRAW = 2;
private static final int MAX_CIRCLES_TO_DRAW = 10;
private static final int MIN_CIRCLES_TO_DRAW = 6;

@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
doGet(req, resp);
}

@Override
protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
logger.debug("Generating captcha...");

response.setContentType(IMAGE_MIME_TYPE_JPG);
try {

Color backgroundColor = new Color(240, 244, 247);

Color textColor = new Color(131, 153, 184);

Color circleColor = new Color(195, 208, 247);
Font textFont = new Font(CAPTCHA_FONT, Font.PLAIN, 24);
int charsToPrint = 5;
int width = request.getParameter(REQUEST_PARAM_WIDTH) != null ? Integer.parseInt(request
.getParameter(REQUEST_PARAM_WIDTH)) : 150;
int height = request.getParameter(REQUEST_PARAM_HEIGHT) != null ? Integer.parseInt(request
.getParameter(REQUEST_PARAM_HEIGHT)) : 30;

float horizMargin = 20.0f;
float imageQuality = 0.95f; // max is 1.0 (this is for jpeg)
double rotationRange = 0.7; // this is radians
BufferedImage bufferedImage = new BufferedImage(width, height, BufferedImage.TYPE_INT_RGB);

Graphics2D g = (Graphics2D) bufferedImage.getGraphics();
g.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON);
// Draw an oval
g.setColor(backgroundColor);
g.fillRect(0, 0, width, height);

// lets make some noisy circles
int circlesToDraw = (int) (Math.random() * (MAX_CIRCLES_TO_DRAW - MIN_CIRCLES_TO_DRAW))
+ MIN_CIRCLES_TO_DRAW;

for (int i = 0; i < circlesToDraw; i++) {
g.setColor((i % 2 == 0) ? (circleColor) : (new Color(circleColor.getRed(), 123 + (int) (Math.random() * 122),
circleColor.getGreen())));

int circleWidth = (int) ((Math.random() * width / 2.0) * (Math.random() * 2));
int circleHeight = (int) ((Math.random() * height / 2.0) * (Math.random() * 2));
int circleX = (int) (Math.random() * width - circleWidth);
int circleY = (int) (Math.random() * height - circleHeight);

g.drawOval(circleX, circleY, circleWidth, circleHeight);
}

// // lets make some noisy lines
// int linesToDraw = (int) (Math.random() * (MAX_LINES_TO_DRAW - MIN_LINES_TO_DRAW)) + MIN_LINES_TO_DRAW;
// for (int i = 0; i < linesToDraw; i++) {
// g.setColor((i % 2 == 0) ? (textColor) : (new Color(textColor.getRed(), (int) (Math.random() * 255),
// textColor.getGreen())));
//
// g.drawLine((int) (Math.random() * width), (int) (Math.random() * height),
// (int) (Math.random() * width), (int) (Math.random() * height));
// }

g.setColor(textColor);
g.setFont(textFont);

FontMetrics fontMetrics = g.getFontMetrics();
int maxAdvance = fontMetrics.getMaxAdvance();
int fontHeight = fontMetrics.getHeight();

// i removed 1 and l and i because there are confusing to users...
// Z, z, and N also get confusing when rotated
// 0, O, and o are also confusing...
// lowercase G looks a lot like a 9 so i killed it
// this should ideally be done for every language...
// i like controlling the characters though because it helps prevent confusion
String elegibleChars = "123456789";
char[] chars = elegibleChars.toCharArray();

float spaceForLetters = -horizMargin * 2 + width;
float spacePerChar = spaceForLetters / (charsToPrint - 1.0f);

StringBuffer finalString = new StringBuffer();

for (int i = 0; i < charsToPrint; i++) {
double randomValue = Math.random();
int randomIndex = (int) Math.round(randomValue * (chars.length - 1));

char characterToShow = chars[randomIndex];
if (i == 2) {
characterToShow = '+';
} else if (i == 4) {
characterToShow = '=';
}
finalString.append(characterToShow);

// this is a separate canvas used for the character so that
// we can rotate it independently
int charWidth = fontMetrics.charWidth(characterToShow);
int charDim = Math.max(maxAdvance, fontHeight);
int halfCharDim = (charDim / 2);

BufferedImage charImage = new BufferedImage(charDim, charDim, BufferedImage.TYPE_INT_ARGB);
Graphics2D charGraphics = charImage.createGraphics();
charGraphics.translate(halfCharDim, halfCharDim);
double angle = (Math.random() - 0.5) * rotationRange;
if (!(characterToShow == '+' || characterToShow == '=')) {
charGraphics.transform(AffineTransform.getRotateInstance(angle));
}
charGraphics.translate(-halfCharDim, -halfCharDim);
charGraphics.setColor(textColor);
charGraphics.setFont(textFont);

int charX = (int) (0.5 * charDim - 0.5 * charWidth);
charGraphics.drawString("" + characterToShow, charX,
((charDim - fontMetrics.getAscent()) / 2 + fontMetrics.getAscent()));

float x = horizMargin + spacePerChar * (i) - charDim / 2.0f;
int y = ((height - charDim) / 2);
// System.out.println("x=" + x + " height=" + height + " charDim=" + charDim + " y=" + y + " advance=" +
// maxAdvance + " fontHeight=" + fontHeight + " ascent=" + fontMetrics.getAscent());
g.drawImage(charImage, (int) x, y, charDim, charDim, null, null);

charGraphics.dispose();
}

// Write the image as a jpg
Iterator<ImageWriter> iter = ImageIO.getImageWritersByFormatName("JPG");
if (iter.hasNext()) {
ImageWriter writer = iter.next();
ImageWriteParam iwp = writer.getDefaultWriteParam();
iwp.setCompressionMode(ImageWriteParam.MODE_EXPLICIT);
iwp.setCompressionQuality(imageQuality);
writer.setOutput(ImageIO.createImageOutputStream(response.getOutputStream()));
IIOImage imageIO = new IIOImage(bufferedImage, null, null);
writer.write(null, imageIO, iwp);
} else {
logger.error("doGet(HttpServletRequest, HttpServletResponse) - no encoder found for jsp.");
throw new RuntimeException("no encoder found for jsp");
}
// ImageIO.write(bufferedImage, "jpg", response.getOutputStream());

// let's stick the final string in the session
int firstDigit = Integer.parseInt(finalString.substring(0, 2));
int secoundDigit = Integer.parseInt(finalString.substring(3, 4));
int result = firstDigit + secoundDigit;

logger.debug("Generated captcha code:" + result);

request.getSession().setAttribute(SESSION_PARAM_CAPTCHA_IMAGE, String.valueOf(result));

g.dispose();
response.flushBuffer();
} catch (IOException ioe) {
logger.error("doGet(HttpServletRequest, HttpServletResponse)", ioe);
throw new RuntimeException("Unable to build image", ioe);
}

}

}

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