[Tutorial] Home made Captcha w/ user input

Things you'll need
1. Picture box (To display the captcha image)
2. Two buttons (Refresh, and submitting answer)
3. Textbox (To type in the captcha answer)

To start out, right bellow Public Class Form1, put

Code:
Private GetAnswer As String = Nothing

Next we're going to make a function, which will create the captcha's question

Code:
Private Function QuestionMaker() As String
        Dim OperatorsC As String() = {"+", "-"}
Start:
        Dim Num1 As Integer = New Random().Next(1, 9)
        Dim Num2 As Integer = New Random().Next(1, 9)

        If Num1 = Num2 Then GoTo Start

        Dim OperatorC2 As String = OperatorsC(New Random().Next(0, OperatorsC.Length))

        Select Case OperatorC2
            Case "+"
                GetAnswer = Num1 + Num2
                If GetAnswer <= 0 Then GoTo Start
            Case "-"
                GetAnswer = Num1 - Num2
                If GetAnswer <= 0 Then GoTo Start
        End Select
        Return String.Format("{0}{1}{2}", Num1, OperatorC2, Num2)
    End Function

Next we're going to create a private sub which will generate random lines around the captcha image

Code:
Private Sub CreateTheLines(ByVal G As Graphics)
        If Not G Is Nothing Then
            Dim R As New Random()
            Dim lineBrush As New SolidBrush(Color.LightGray)

            For i% = 0 To 9
                G.DrawLines(New Pen(lineBrush, R.Next(1, 2)), New Point() {New Point(0, R.Next(0, 60)), New Point(200, R.Next(0, 60))})

            Next
        End If
    End Sub

and finally we will create the function for generating the image itself.

Code:
Private Function ImageCreation() As Image
        Dim B As New Bitmap(200, 60)
        Using G As Graphics = Graphics.FromImage(B)
            With G
                .Clear(Color.White)
                .DrawString(QuestionMaker(), New Font("Verdana", 20), Brushes.Black, New Rectangle(0, 0, 200, 60), New StringFormat() With {.Alignment = StringAlignment.Center, .LineAlignment = StringAlignment.Center})
            End With
            CreateTheLines(G)
        End Using
        Return B
    End Function

Usage for this would be like this, The Submit button would have this code

Code:
Select Case TextBox1.Text
            Case Is = GetAnswer

                MessageBox.Show("Correct!", "Correct!", MessageBoxButtons.OK, MessageBoxIcon.Asterisk)
                PictureBox1.Image = ImageCreation()
                TextBox1.Clear()
            Case Else
                MessageBox.Show("Incorrect!", "Incorrect!", MessageBoxButtons.OK, MessageBoxIcon.Asterisk)
                PictureBox1.Image = ImageCreation()
                TextBox1.Clear()
        End Select

The Refresh button would be this

Code:
PictureBox1.Image = ImageCreation()

and formload sub would contain this as well

Code:
PictureBox1.Image = ImageCreation()

Hope you enjoyed this tutorial!

Picture from Platinum:
[Image: ivb3.png]