--Sample code
//Captcha.ashx.cs
using System;
using System.Web;
using System.Drawing;
using System.IO;
using System.Web.SessionState;
using System.Drawing.Imaging;
using System.Drawing.Text;
using System.Drawing.Drawing2D;
namespace CAPTCHADrawing
{
/// <summary>
/// Summary description for Captcha
/// </summary>
public class Captcha : IHttpHandler, IReadOnlySessionState
{
public void ProcessRequest(HttpContext context)
{
int iHeight = 80;
int iWidth = 190;
Random oRandom = new Random();
int[] aBackgroundNoiseColor = new int[] { 150, 150, 150 };
int[] aTextColor = new int[] { 0, 0, 0 };
int[] aFontEmSizes = new int[] { 15, 20, 25, 30, 35 };
string[] aFontNames = new string[] { "Comic Sans MS", "Arial", "Times New Roman", "Georgia", "Verdana", "Geneva"};
FontStyle[] aFontStyles = new FontStyle[] { FontStyle.Bold, FontStyle.Italic, FontStyle.Regular, FontStyle.Strikeout, FontStyle.Underline};
HatchStyle[] aHatchStyles = new HatchStyle[]
{
HatchStyle.BackwardDiagonal, HatchStyle.Cross,
HatchStyle.DashedDownwardDiagonal, HatchStyle.DashedHorizontal,
HatchStyle.DashedUpwardDiagonal, HatchStyle.DashedVertical,
HatchStyle.DiagonalBrick, HatchStyle.DiagonalCross,
HatchStyle.Divot, HatchStyle.DottedDiamond, HatchStyle.DottedGrid,
HatchStyle.ForwardDiagonal, HatchStyle.Horizontal,
HatchStyle.HorizontalBrick, HatchStyle.LargeCheckerBoard,
HatchStyle.LargeConfetti, HatchStyle.LargeGrid,
HatchStyle.LightDownwardDiagonal, HatchStyle.LightHorizontal,
HatchStyle.LightUpwardDiagonal, HatchStyle.LightVertical,
HatchStyle.Max, HatchStyle.Min, HatchStyle.NarrowHorizontal,
HatchStyle.NarrowVertical, HatchStyle.OutlinedDiamond,
HatchStyle.Plaid, HatchStyle.Shingle, HatchStyle.SmallCheckerBoard,
HatchStyle.SmallConfetti, HatchStyle.SmallGrid,
HatchStyle.SolidDiamond, HatchStyle.Sphere, HatchStyle.Trellis,
HatchStyle.Vertical, HatchStyle.Wave, HatchStyle.Weave,
HatchStyle.WideDownwardDiagonal, HatchStyle.WideUpwardDiagonal, HatchStyle.ZigZag
};
//Get Captcha in Session
string sCaptchaText = context.Session["Captcha"].ToString();
//Creates an output Bitmap
Bitmap oOutputBitmap = new Bitmap(iWidth, iHeight, PixelFormat.Format24bppRgb);
Graphics oGraphics = Graphics.FromImage(oOutputBitmap);
oGraphics.TextRenderingHint = TextRenderingHint.AntiAlias;
//Create a Drawing area
RectangleF oRectangleF = new RectangleF(0, 0, iWidth, iHeight);
Brush oBrush = default(Brush);
//Draw background (Lighter colors RGB 100 to 255)
oBrush = new HatchBrush(aHatchStyles[oRandom.Next
(aHatchStyles.Length - 1)], Color.FromArgb((oRandom.Next(100, 255)),
(oRandom.Next(100, 255)), (oRandom.Next(100, 255))), Color.White);
oGraphics.FillRectangle(oBrush, oRectangleF);
System.Drawing.Drawing2D.Matrix oMatrix = new System.Drawing.Drawing2D.Matrix();
int i = 0;
for (i = 0; i <= sCaptchaText.Length - 1; i++)
{
oMatrix.Reset();
int iChars = sCaptchaText.Length;
int x = iWidth / (iChars + 1) * i;
int y = iHeight / 2;
//Rotate text Random
oMatrix.RotateAt(oRandom.Next(-40, 40), new PointF(x, y));
oGraphics.Transform = oMatrix;
//Draw the letters with Random Font Type, Size and Color
oGraphics.DrawString
(
//Text
sCaptchaText.Substring(i, 1),
//Random Font Name and Style
new Font(aFontNames[oRandom.Next(aFontNames.Length - 1)],
aFontEmSizes[oRandom.Next(aFontEmSizes.Length - 1)],
aFontStyles[oRandom.Next(aFontStyles.Length - 1)]),
//Random Color (Darker colors RGB 0 to 100)
new SolidBrush(Color.FromArgb(oRandom.Next(0, 100),
oRandom.Next(0, 100), oRandom.Next(0, 100))),
x,
oRandom.Next(10, 40)
);
oGraphics.ResetTransform();
}
MemoryStream oMemoryStream = new MemoryStream();
oOutputBitmap.Save(oMemoryStream, System.Drawing.Imaging.ImageFormat.Png);
byte[] oBytes = oMemoryStream.GetBuffer();
oOutputBitmap.Dispose();
oMemoryStream.Close();
context.Response.BinaryWrite(oBytes);
context.Response.End();
}
public bool IsReusable
{
get
{
return false;
}
}
}
}
//CaptchaImage.aspx design
<%@ Page Language="C#" AutoEventWireup="true" CodeBehind="CaptchaImage.aspx.cs" Inherits="CAPTCHADrawing.CaptchaImage" %>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head runat="server">
<title></title>
</head>
<body>
<form id="form1" runat="server">
<div>
<asp:Image ID="imgCaptcha" ImageUrl="Captcha.ashx" runat="server" />
<asp:TextBox runat="server" ID="txtCaptcha"/>
<asp:Button Text="Submit" runat="server" onclick="Unnamed1_Click" />
</div>
</form>
</body>
</html>
//CaptchaImage.aspx.cs
u
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