Public Class Form1
 
    Dim bm1, bm2 As New Bitmap(100, 100)
    Dim g As Graphics = Graphics.FromImage(bm1)
 
    Private Sub Button3_Click(ByVal sender As System.Object, ByVal e As _
      System.EventArgs) Handles Button3.Click
        g.Clear(Color.White)
        For i As Int32 = 0 To bm1.Height - 1 Step 2
            g.DrawLine(Pens.Blue, 0, i, bm1.Width, i)
        Next
        bm2 = CType(bm1.Clone, Bitmap)
        g.DrawImage(SystemIcons.Error.ToBitmap, 10, 10)
        g.DrawImage(SystemIcons.Warning.ToBitmap, 50, 50)
        PictureBox1.SetBounds(5, 5, 100, 100)
        PictureBox2.SetBounds(110, 5, 100, 100)
        PictureBox3.SetBounds(215, 5, 100, 100)
        PictureBox1.Image = bm1
        PictureBox2.Image = bm2
        PictureBox3.Image = BitmapDiff(bm1, bm2)
 
    End Sub
 
 Private Function BitmapDiff(ByVal b1 As Bitmap, ByVal b2 As Bitmap) As Bitmap
        Dim bm As New Bitmap(b1.Width, b1.Height)
        For y As Integer = 0 To b1.Height - 1
            For x As Integer = 0 To b1.Width - 1
                If b1.GetPixel(x, y) <> b2.GetPixel(x, y) Then
                    bm.SetPixel(x, y, b1.GetPixel(x, y))
                End If
            Next
        Next
        Return bm
    End Function
 
 
    Private Sub ComboBox1_SelectedIndexChanged(ByVal sender As System.Object, _
      ByVal e As System.EventArgs) Handles ComboBox1.SelectedIndexChanged
        Me.PictureBox1.BackgroundImageLayout = _
        System.Windows.Forms.ImageLayout.None
        Me.PictureBox1.Load(ComboBox1.SelectedItem)
        Me.PictureBox1.Refresh()
        bm1 = Me.PictureBox1.Image
 
    End Sub
 
    Private Sub ComboBox2_SelectedIndexChanged(ByVal sender As System.Object, _
      ByVal e As System.EventArgs) Handles ComboBox2.SelectedIndexChanged
        Me.PictureBox2.BackgroundImageLayout = _
        System.Windows.Forms.ImageLayout.None
        Me.PictureBox2.Load(ComboBox2.SelectedItem)
        Me.PictureBox2.Refresh()
        bm2 = Me.PictureBox2.Image
    End Sub
End Class