Imports System.Runtime.InteropServices.Marshal
Imports System.Drawing.Imaging
Public Class Form1
    Dim bmp1 As New System.Drawing.Bitmap("C:\W-Intern\GPM.jpg")   ' 680x680 
    ' Pixel 
    Dim bmp2 As Bitmap = bmp1.Clone
    Function BmpDiff(ByVal b1 As Bitmap, ByVal b2 As Bitmap) As Int32
        If b1.Size <> b2.Size Then Return -1
        Dim rect As New Rectangle(0, 0, b1.Width, b1.Height)                    _
                   'bm-Abmessung
        Dim bd1 As BitmapData = b1.LockBits(rect, ImageLockMode.ReadWrite, _
        PixelFormat.Format24bppRgb)
        Dim bd2 As BitmapData = b2.LockBits(rect, ImageLockMode.ReadWrite, _
        PixelFormat.Format24bppRgb)
        Dim max As Int32 = (bd1.Stride * b1.Height) - 1                         _
                 ' (zeile*h)-1
        Dim fw1(max) As Byte, fw2(max) As Byte
        Copy(bd1.Scan0, fw1, 0, max)                                            _
                   ' bm ins array
        Copy(bd2.Scan0, fw2, 0, max)
        b2.UnlockBits(bd2)                                                      _
                   ' Sperre aufheben
        b1.UnlockBits(bd1)
        Dim diff As Int32                                                       _
                   ' Abweichung
        For x As Int32 = 0 To max - 3 Step 3
            If fw1(x) <> fw2(x) OrElse fw1(x + 1) <> fw2(x + 1) OrElse _
              fw1(x + 2) <> fw2(x + 2) Then
                diff += 1
            End If
        Next x
        Return diff
    End Function
 
    Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As _
      System.EventArgs) Handles Button1.Click       
        Me.Text = BmpDiff(bmp1, bmp2).ToString()
    End Sub
End Class