<%@ WebHandler Language="C#" Class="HipHandler" %>

 

using System;

using System.Web;

using System.Drawing;

using System.Drawing.Imaging;

using System.Drawing.Drawing2D;

using System.Drawing.Text;

 

public class HipHandler : IHttpHandler {

 

    public void ProcessRequest (HttpContext context) {

        context.Response.ContentType = "image/jpeg";

        SendImage(context);

    }

 

    public void SendImage(HttpContext context)

    {

        int fontSize = 24;                

        int width = 100;

        int height = 30;

 

        // Setup the rectangle to draw the text on

        RectangleF rectF = new RectangleF(0, 0, width, height);

        Bitmap pic = new Bitmap(width, height);

        Graphics g = Graphics.FromImage(pic);

        g.SmoothingMode = SmoothingMode.AntiAlias;                

        SolidBrush fgBrush = new SolidBrush(Color.Gold);

        SolidBrush bgBrush = new SolidBrush(Color.CornflowerBlue);

        g.FillRectangle(bgBrush, rectF);

 

        // Choose the font and style

        FontStyle style = FontStyle.Regular;        

        Font font = new Font("Arial", fontSize, style, GraphicsUnit.Pixel);

 

        // Make sure the text is centered

        StringFormat format = new StringFormat();

        format.Alignment = StringAlignment.Center;

 

        // Draw horizontal and vertical lines to make is less computer-readable

        Pen p = new Pen(new SolidBrush(Color.SteelBlue), 1);

        for (int i = 0; i < height; i=i+7)

        {

            g.DrawLine(p, 0, i, width, i);    

        }

 

        for (int i = 0; i < width; i=i+10)

        {

            g.DrawLine(p, i, 0, i, height);    

        }

 

        // Get 4 random characters, no weird ones

        string randomText = GenerateRandomText(4, false);

        System.Security.Cryptography.SHA256Managed hashAlg = new System.Security.Cryptography.SHA256Managed();

 

        // Hash the text so it can be verified after postback

        string hashText = HttpUtility.UrlEncode(hashAlg.ComputeHash(System.Text.Encoding.Default.GetBytes(randomText)));

        context.Response.AppendCookie(new HttpCookie("HipHash", hashText));

 

        // Write the text and send it to the browser

        g.DrawString(randomText, font, fgBrush, rectF, format);        

        pic.Save(context.Response.OutputStream, ImageFormat.Jpeg);        

    }

 

    public static string GenerateRandomText(int maxlength, bool ultraStrong)

    {

        char[] ultraChars = "!@#$%^&*~|=?{}[]qwertyuiopasdfghjklzxcvbnm1234567890!@#$%^&*~|=?{}[]".ToCharArray();

        char[] normalChars = "qwertyuiopasdfghjklzxcvbnm1234567890".ToCharArray();

 

        string password = string.Empty;

        for (int i = 0; i < maxlength; i++)

        {

            char n = ' ';

            if (ultraStrong) n = ultraChars[GetRandomNumber(ultraChars.Length - 1)];

            if (!ultraStrong) n = normalChars[GetRandomNumber(normalChars.Length - 1)];

            if (i % 2 == 0)

                password += n.ToString().ToUpper();

            else

                password += n;

        }

        return password;

    }

 

    public static int GetRandomNumber(int maxvalue)

    {

        System.Security.Cryptography.RandomNumberGenerator random =

            System.Security.Cryptography.RandomNumberGenerator.Create();

 

        byte[] r = new byte[1];

        random.GetBytes(r);

        double val = (double)r[0] / byte.MaxValue;

        int i = (int)Math.Round(val * maxvalue, 0);

        return i;

    }

 

    public bool IsReusable {

        get {

            return false;

        }

    }

}