Public Class Form1
    Dim gambar2 As Bitmap
    Private Sub Form1_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load
        PictureBox2.Image = PictureBox1.Image
    End Sub

    Private Sub btngrayscale_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles btngrayscale.Click
        Dim Pb, Pc As Integer
        Dim Rt, vM, vH, vB As Double
        gambar2 = New Bitmap(PictureBox2.Image)
        For Pb = 0 To gambar2.Height - 1
            For Pc = 0 To gambar2.Width - 1
                vM = gambar2.GetPixel(Pc, Pb).R
                vH = gambar2.GetPixel(Pc, Pb).G
                vB = gambar2.GetPixel(Pc, Pb).B
                Rt = (vM + vH + vB) / 3
                gambar2.SetPixel(Pc, Pb, Color.FromArgb(Rt, Rt, Rt))
            Next
            PictureBox2.Image = gambar2
            PictureBox2.Refresh()
        Next
    End Sub
End Class