Generating a dynamic registration image for web application registration page

This focuses on generating an image on the fly in ASP.NET. This feature you may find on any website that requires registration of a user. Example: Yahoo Registration, this site requires you to type in your secret string before you can successfully login.

This focuses on generating an image on the fly in ASP.NET. This feature you may find on any website that requires registration of a user. Example: Yahoo Registration, this site requires you to type in your secret string before you can successfully login.

Step 1: Create a new web application

Step 2: Open Code Behind Form of web application you have created.

Step 3: Add Namespace for drawing Image.

using System.Drawing;
using System.Drawing.Imaging;

Step 4: Write the Code for Generating a Random Registration String (Here: Generating Random string of 10 characters in length).

    // Generate a random password with the specified length. The password will only 
    // contain digits and letters (either lowercase or uppercase)
    public static string GetRandomPassword(int length)
    {
        Random rand = new Random();
        System.Text.StringBuilder password = new System.Text.StringBuilder(length);
        for (int i = 1; i <= length; i++)
        {
            int charIndex;
            // allow only digits and letters
            do
            {
                charIndex = rand.Next(48, 123);
            } while (!((charIndex >= 48 && charIndex <= 57) ||
            (charIndex >= 65 && charIndex <= 90) || (charIndex >= 97 && charIndex <= 122)));


            // add the random char to the password being built
            password.Append(Convert.ToChar(charIndex)); 

        }
        return password.ToString();
    }

Step 5: Write Code for Generating Image. This code will create RegistrationImg.gif in your application folder.

    //Generate Image
    private void GenerateImage(string strRegistrationStr)
    {
        Bitmap objBitmap = new Bitmap(150, 30);
        Graphics objGraphics = Graphics.FromImage(objBitmap);
 

        //Fore Color and Background of Image
        SolidBrush objForeColor = new SolidBrush(Color.White);
        SolidBrush objBackColor = new SolidBrush(Color.Black);
 
        objGraphics.FillRectangle(objBackColor, 0, 0, 150, 30); 

        //Font settings for Image
        Font objFont = new Font("Arial", 15); 

        //Display from 5point from x-axis and 5point from y-axis
        Point objPoint = new Point(5, 5); 

        //Drawing Registration String
        objGraphics.DrawString(strRegistrationStr, objFont, objForeColor, objPoint);

        //Saving Registration String as Image
        //If you dont want image to save
        //objBitmap.Save(Response.OutputStream, ImageFormat.Gif);
        //otherwise use this
        objBitmap.Save(Server.MapPath("RegistrationImg.gif"), ImageFormat.Gif);        


        //Release object
        if(objBitmap != null)
            objBitmap.Dispose();
        if (objGraphics != null)
            objGraphics.Dispose();
    }

Step 6: Finally the code for calling the created functionality.

   protected void btnShowRegistrationImg_Click(object sender, EventArgs e)
    {
        GenerateImage(GetRandomPassword(10));
        ImgRegistrationStr.ImageUrl = "RegistrationImg.gif";
    }

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