CAPTCHA (Completely Automated Public Turing test to tell Computers and Humans Apart) images are those distorted pictures of words that some Web sites make you enter to prove you are a human and not an automated process. The idea is to distort the characters in the image so it would be hard for an optical character recognition (OCR) application to read them but so it would still be easy for a person to read them.

Subroutine DrawCaptcha is quick and simple. It merely draws two strings on top of each other. Usually a human can still read them.

' Draw the words overlaid on each other.
Private Sub DrawCaptcha(ByVal pic As PictureBox, ByVal _
    word1 As String, ByVal word2 As String)
Dim x As Single
Dim y As Single

    Randomize

    ' Draw the first word, offset horizontally by a random
    ' amount.
    x = Rnd * (pic.ScaleWidth - pic.TextWidth(word1))
    pic.CurrentX = x
    pic.CurrentY = 0
    pic.Print word1

    ' Draw the second word over the first,
    ' offset vertically a bit and horizontally
    ' by a random amount.
    x = Rnd * (pic.ScaleWidth - pic.TextWidth(word2))
    y = pic.TextHeight(word2) / 3
    If y > pic.ScaleHeight - pic.TextHeight(word2) Then _
        y = pic.ScaleHeight - pic.TextHeight(word2)
    pic.CurrentX = x
    pic.CurrentY = y
    pic.Print word2
End Sub