Option Explicit

Private Sub Command1_Click()
    Dim x As Long
    Dim y As Long
    Dim c As Long
    Dim r, g, b As Byte

    Picture1.Picture = LoadPicture("d:\disegni\fridgedoor_1683_28908208.gif")
    'convert picture lo grayscale
    With Picture1
    For x = 1 To .ScaleX(.Picture.Width, vbHimetric, vbPixels)
        For y = 1 To .ScaleY(.Picture.Height, vbHimetric, vbPixels)
            c = .Point(.ScaleX(x, vbPixels, .ScaleMode), .ScaleY(y, vbPixels, .ScaleMode))
            If c > 0 Then
                b = c Mod 256
                c = c \ 256
                g = c Mod 256
                r = c \ 256
                c = (r + g + b) / 3
                Picture1.PSet (.ScaleX(x, vbPixels, .ScaleMode), .ScaleY(y, vbPixels, .ScaleMode)), RGB(c, c, c)
            End If
        Next
    Next
    End With
End Sub



From this, how to convert gray scale to threshold, smoothing filter, Convolution – Laplacian sharpening filter (3x3 mask),Edge detection – Sobel kernel (3x3 mask), inverse.