DZone Snippets: Captcha code

CaptchaImage

mstampar (Miroslav Stampar) — Wed, 09 May 2007 23:18:27 GMT



    public class CaptchaImage

    {

        // Public properties (all read-only).

        public string Text

        {

            get { return this.text; }

        }

        public Bitmap Image

        {

            get { return this.image; }

        }

        public int Width

        {

            get { return this.width; }

        }

        public int Height

        {

            get { return this.height; }

        }



        // Internal properties.

        private string text;

        private int width;

        private int height;

        private string familyName;

        private Bitmap image;



        // For generating random numbers.

        private Random random = new Random();



        // ====================================================================

        // Initializes a new instance of the CaptchaImage class using the

        // specified text, width and height.

        // ====================================================================

        public CaptchaImage(int length, int width, int height) : this(length, width, height, null)

        {

        }



        // ====================================================================

        // Initializes a new instance of the CaptchaImage class using the

        // specified text, width, height and font family.

        // ====================================================================

        public CaptchaImage(int length, int width, int height, string familyName)

        {

            this.text = GenerateRandomText(length);

            this.SetDimensions(width, height);

            this.SetFamilyName(familyName);

            this.GenerateImage();

        }



        private string GenerateRandomText(int length)

        {

            Random rnd = new Random();

            List table = new List();



            for (char i = 'A'; i <= 'Z'; i++)

                table.Add(i);



            for (char i = '0'; i <= '9'; i++)

                table.Add(i);



            string retVal = "";

            

            for (int i = 0; i < length; i++)

                retVal += table[rnd.Next(table.Count)];



            return retVal;

        }



        // ====================================================================

        // This member overrides Object.Finalize.

        // ====================================================================

        ~CaptchaImage()

        {

            Dispose(false);

        }



        // ====================================================================

        // Releases all resources used by this object.

        // ====================================================================

        public void Dispose()

        {

            GC.SuppressFinalize(this);

            this.Dispose(true);

        }



        // ====================================================================

        // Custom Dispose method to clean up unmanaged resources.

        // ====================================================================

        protected virtual void Dispose(bool disposing)

        {

            if (disposing)

                // Dispose of the bitmap.

                this.image.Dispose();

        }



        // ====================================================================

        // Sets the image width and height.

        // ====================================================================

        private void SetDimensions(int width, int height)

        {

            // Check the width and height.

            if (width <= 0)

                throw new ArgumentOutOfRangeException("width", width, "Argument out of range, must be greater than zero.");

            if (height <= 0)

                throw new ArgumentOutOfRangeException("height", height, "Argument out of range, must be greater than zero.");

            this.width = width;

            this.height = height;

        }



        // ====================================================================

        // Sets the font used for the image text.

        // ====================================================================

        private void SetFamilyName(string familyName)

        {

            // If the named font is not installed, default to a system font.

            try

            {

                Font font = new Font(this.familyName, 12F);

                this.familyName = familyName;

                font.Dispose();

            }

            catch (Exception ex)

            {

                this.familyName = System.Drawing.FontFamily.GenericSerif.Name;

            }

        }



        // ====================================================================

        // Creates the bitmap image.

        // ====================================================================

        private void GenerateImage()

        {

            // Create a new 32-bit bitmap image.

            Bitmap bitmap = new Bitmap(this.width, this.height, PixelFormat.Format32bppArgb);



            // Create a graphics object for drawing.

            Graphics g = Graphics.FromImage(bitmap);

            g.SmoothingMode = SmoothingMode.AntiAlias;

            Rectangle rect = new Rectangle(0, 0, this.width, this.height);



            // Fill in the background.

            HatchBrush hatchBrush = new HatchBrush(HatchStyle.SmallConfetti, Color.LightGray, Color.White);

            g.FillRectangle(hatchBrush, rect);



            // Set up the text font.

            SizeF size;

            float fontSize = rect.Height + 1;

            Font font;

            // Adjust the font size until the text fits within the image.

            do

            {

                fontSize--;

                font = new Font(this.familyName, fontSize, FontStyle.Bold);

                size = g.MeasureString(this.text, font);

            } while (size.Width > rect.Width);



            // Set up the text format.

            StringFormat format = new StringFormat();

            format.Alignment = StringAlignment.Center;

            format.LineAlignment = StringAlignment.Center;



            // Create a path using the text and warp it randomly.

            GraphicsPath path = new GraphicsPath();

            path.AddString(this.text, font.FontFamily, (int)font.Style, font.Size, rect, format);

            float v = 4F;

            PointF[] points =

			{

				new PointF(this.random.Next(rect.Width) / v, this.random.Next(rect.Height) / v),

				new PointF(rect.Width - this.random.Next(rect.Width) / v, this.random.Next(rect.Height) / v),

				new PointF(this.random.Next(rect.Width) / v, rect.Height - this.random.Next(rect.Height) / v),

				new PointF(rect.Width - this.random.Next(rect.Width) / v, rect.Height - this.random.Next(rect.Height) / v)

			};

            Matrix matrix = new Matrix();

            matrix.Translate(0F, 0F);

            path.Warp(points, rect, matrix, WarpMode.Perspective, 0F);



            // Draw the text.

            hatchBrush = new HatchBrush(HatchStyle.LargeConfetti, Color.LightGray, Color.DarkGray);

            g.FillPath(hatchBrush, path);



            // Add some random noise.

            int m = Math.Max(rect.Width, rect.Height);

            for (int i = 0; i < (int)(rect.Width * rect.Height / 30F); i++)

            {

                int x = this.random.Next(rect.Width);

                int y = this.random.Next(rect.Height);

                int w = this.random.Next(m / 50);

                int h = this.random.Next(m / 50);

                g.FillEllipse(hatchBrush, x, y, w, h);

            }



            // Clean up.

            font.Dispose();

            hatchBrush.Dispose();

            g.Dispose();



            // Set the image.

            this.image = bitmap;

        }

    }

100 Line Captcha JSP

hebbar (ravindra) — Fri, 09 Feb 2007 13:26:31 GMT

// description of your code here



100 Line Captcha JSP





Simple, nice looking captcha implemented in 100 lines of JSP. Easily change font, colors, size, and captcha characters. Since it's a JSP you can rewrite it to do whatever the heck you want to do. Enjoy!!! ...and send me any improvements you make



<%@ page import="java.util.*"%>

<%@ page import="java.io.*"%>

<%@ page import="javax.servlet.*"%>

<%@ page import="javax.servlet.http.*"%>

<%@ page import="java.awt.*"%>

<%@ page import="java.awt.image.*"%>

<%@ page import="javax.imageio.*"%>

<%@ page import="java.awt.geom.*"%>

<%

 //========================================================

 // Kick Ass Captcha JSP

 //

 // Michael Connor 2007

 //

 // I just couldn't handle the thought of downloading a

 // big jar and configuring some servlet.xml and having

 // little to no control of anything...

 // You can send in height and width parameters.

 // The captcha value will be placed in the session in

 // a parameter called 'captcha'

 //

 // Feel free to use this code and do whatever the hell

 // you want to it.

 //========================================================



 response.setContentType("image/jpg");



 try {

   

   Color backgroundColor = Color.red;

   Color borderColor = Color.red;

   Color textColor = Color.white;

   Color circleColor = new Color(160,160,160);

   Font textFont = new Font("Arial", Font.PLAIN, 24);

   int charsToPrint = 6;

   int width = request.getParameter("width") != null ? Integer.parseInt(request.getParameter("width")) : 150;

   int height = request.getParameter("height") != null ? Integer.parseInt(request.getParameter("height")) : 80;

   int circlesToDraw = 4;

   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();



   //Draw an oval

   g.setColor(Color.red);

   g.fillRect(0, 0, width, height);



   // lets make some noisey circles

   g.setColor(circleColor);

   for ( int i = 0; i < circlesToDraw; i++ ) {

     int circleRadius = (int) (Math.random() * height / 2.0);

     int circleX = (int) (Math.random() * width - circleRadius);

     int circleY = (int) (Math.random() * height - circleRadius);

     g.drawOval(circleX, circleY, circleRadius * 2, circleRadius * 2);

   }



   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 = "ABCDEFGHJKLMPQRSTUVWXYabcdefhjkmnpqrstuvwxy23456789";

   char[] chars = elegibleChars.toCharArray();



   float spaceForLetters = -horizMargin * 2 + width;

   float spacePerChar = spaceForLetters / (charsToPrint - 1.0f);



   AffineTransform transform = g.getTransform();



   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];

     finalString.append(characterToShow);



     // this is a separate canvas used for the character so that

     // we can rotate it independently

     int charImageWidth = maxAdvance * 2;

     int charImageHeight = fontHeight * 2;

     int charWidth = fontMetrics.charWidth(characterToShow);

     int charDim = Math.max(maxAdvance, fontHeight);

     int halfCharDim = (int) (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;

     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, 

                            (int) ((charDim - fontMetrics.getAscent()) 

                                   / 2 + fontMetrics.getAscent()));



     float x = horizMargin + spacePerChar * (i) - charDim / 2.0f;

     int y = (int) ((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 iter = ImageIO.getImageWritersByFormatName("JPG");

   if( iter.hasNext() ) {

     ImageWriter writer = (ImageWriter)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 {

     throw new RuntimeException("no encoder found for jsp");

   }



   // let's stick the final string in the session

   request.getSession().setAttribute("captcha", finalString.toString());



   g.dispose();

 } catch (IOException ioe) {

   throw new RuntimeException("Unable to build image" , ioe);

 }

%>