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By ale73 at 2012-02-15

To provide a captcha system I have created the following step

Create a rectangle

Create random number from 1 to 10000
Add random lines across the rectangle

Add random point across the rectangle

using System.Drawing and System.Drawing.Image here is the code in Page looa of Default.aspx.cs

protected void Page_Load(object sender, EventArgs e)
{

Response.ContentType = "image/png";

Random r= new Random();
int numr = r.Next(100000);
Bitmap img = new Bitmap(400, 100);
Graphics g = Graphics.FromImage(img);
g.FillRectangle(Brushes.Blue, 0, 0, 400, 200);
Font f = new Font("Arial", 30);
g.DrawString(Convert.ToString(numr), f, Brushes.White, 120, 20);
Pen p = new Pen(Color.Yellow, 2);
Random rp = new Random();
Random r2 = new Random();

int n = r2.Next(0, 5);
for (int i = 0; i <= n; i++)
{
int nrp = rp.Next(0, 100);

g.DrawLine(p, 0, nrp, 400, nrp);
}
int numpunti = r2.Next(0, 500);
System.Drawing.Image imgp = System.Drawing.Image.FromFile(Server.MapPath("puntorosso2.png"));
for (int j = 0; j < numpunti; j++)
{
int x1 = rp.Next(0, 400);
int y1 = rp.Next(0, 100);
g.DrawImage(imgp, x1, y1);
}
img.Save(Response.OutputStream, ImageFormat.Png);
g.Dispose();
img.Dispose();
imgp.Dispose();
Response.End();
}

if you want iclude in your page, you can do this by

here is the code to download

captcha.rar

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