[VB.NET]Creating a Basic Captcha String

[1UP DF Member Posts:22 Threads:20 Reputation 0]

This was something I pulled from a test program I was messing with. I was writing an application to send some information to a remote database and to prevent "flooding" I could write in a captcha. Granted I would never include this because of how simple it is, it was rather easy.

First off our function to create the random string of letters.

Code:

Private Function generateCaptchaString()
        Dim rand As New Random
        Dim currentLetter As String
        Dim captchaString As String = ""
        For i = 0 To 6
            currentLetter = ChrW(rand.Next(Asc("A"), Asc("Z") + 1))
            captchaString &= currentLetter
        Next

        Return captchaString
    End Function

Then the code for creating the image with the string as apart of it.

Code:

'Set captchaText to what is generated in the function generateRandomString
        Dim captchaText As String = generateCaptchaString()

        'Creating a bitmap in memory
        Dim captchaBitmap As New Bitmap(200, 40)

        'Creating a Graphic so we can manipulate how the image will look
        Dim captchaGraphic As Graphics = Graphics.FromImage(captchaBitmap)

        Dim captchaFont As New Font("Arial", 14)

        'Set the Text color
        Dim captchaForeColor As New SolidBrush(Color.Blue)

        'Set the background color
        Dim captchaBackgroundColor As New SolidBrush(Color.Yellow)

        captchaGraphic.FillRectangle(captchaBackgroundColor, 0, 0, Width, Height)
        captchaGraphic.DrawString(captchaText, captchaFont, captchaForeColor, 5.0F, 5.0F)

        pict_Captcha.Image = captchaBitmap

[Red Painting the town Red Posts:3,756 Threads:228 Reputation 92]

This was something I pulled from a test program I was messing with. I was writing an application to send some information to a remote database and to prevent "flooding" I could write in a captcha. Granted I would never include this because of how simple it is, it was rather easy.

First off our function to create the random string of letters.

Code:

   Private Function generateCaptchaString()
       Dim rand As New Random
       Dim currentLetter As String
       Dim captchaString As String = ""
       For i = 0 To 6
           currentLetter = ChrW(rand.Next(Asc("A"), Asc("Z") + 1))
           captchaString &= currentLetter
       Next

       Return captchaString
   End Function

Then the code for creating the image with the string as apart of it.

Code:

       'Set captchaText to what is generated in the function generateRandomString
       Dim captchaText As String = generateCaptchaString()

       'Creating a bitmap in memory
       Dim captchaBitmap As New Bitmap(200, 40)

       'Creating a Graphic so we can manipulate how the image will look
       Dim captchaGraphic As Graphics = Graphics.FromImage(captchaBitmap)

       Dim captchaFont As New Font("Arial", 14)

       'Set the Text color
       Dim captchaForeColor As New SolidBrush(Color.Blue)

       'Set the background color
       Dim captchaBackgroundColor As New SolidBrush(Color.Yellow)

       captchaGraphic.FillRectangle(captchaBackgroundColor, 0, 0, Width, Height)
       captchaGraphic.DrawString(captchaText, captchaFont, captchaForeColor, 5.0F, 5.0F)

       pict_Captcha.Image = captchaBitmap

This is a very nice tutorial man, very helpful. Thanks for sharing this method.