Dithering form with two colors

[steve65]

I needed to dither my form with two different colors but I didn't see any examples to do that here so I went ahead and threw something together. I hope it helps someone here. If you see anthing I can do to improve the code please let me know. I don't need to be reinventing the wheel but it was fun learning something new.



In a new project add the following

Option Explicit


Public Sub Dither(ByRef vForm As Form, _
                  ByVal SR As Integer, _
                  ByVal SG As Integer, _
                  ByVal SB As Integer, _
                  ByVal ER As Integer, _
                  ByVal EG As Integer, _
                  ByVal EB As Integer)
    
Dim i As Integer
Dim RDelta As Integer
Dim GDelta As Integer
Dim BDelta As Integer
Dim LineR(255) As Integer
Dim LineG(255) As Integer
Dim LineB(255) As Integer
    
    ' Make sure the colors are all valid values.
    If SR < 0 Or SG < 0 Or SB < 0 Or ER < 0 Or EG < 0 Or EB < 0 Then Exit Sub
    If SR > 255 Or SG > 255 Or SB > 255 Or ER > 255 Or EG > 255 Or EB > 255 Then Exit Sub
    
    ' We need To find the largest delta between the starting And ending RGB values.  We need To
    ' scale these up up so they can be stepped through 256 times On one loop.
    RDelta = Abs(SR - ER)
    GDelta = Abs(SG - EG)
    BDelta = Abs(SB - EB)
    
    vForm.ScaleMode = vbPixels
    vForm.DrawWidth = 2
    vForm.ScaleHeight = 256
    
    ' Fill In the color values For the form.
    For i = 0 To 255
        If ER > SR Then
            LineR(i) = SR + (RDelta / 255) * i
        Else
            LineR(i) = SR - (RDelta / 255) * i
        End If
    Next i
    
    For i = 0 To 255
        If EG > SG Then
            LineG(i) = SG + (GDelta / 255) * i
        Else
            LineG(i) = SG - (GDelta / 255) * i
        End If
    Next i
    
    For i = 0 To 255
        If EB > SB Then
            LineB(i) = SB + (BDelta / 255) * i
        Else
            LineB(i) = SB - (BDelta / 255) * i
        End If
    Next i
    
    For i = 0 To 255
        If LineR(i) < 0 Then LineR(i) = 0
        If LineG(i) < 0 Then LineG(i) = 0
        If LineB(i) < 0 Then LineB(i) = 0
        
        If LineR(i) > 255 Then LineR(i) = 255
        If LineG(i) > 255 Then LineG(i) = 255
        If LineB(i) > 255 Then LineB(i) = 255
        
        vForm.Line (0, i)-(Screen.Width, i - 1), RGB(LineR(i), LineG(i), LineB(i)), B
    Next i
    
End Sub

Private Sub Form_Paint()
    Call Dither(Me, 255, 0, 0, 0, 100, 100)
End Sub

[MarkT]

This thread may be of intrest to you http://www.vbforums.com/showthread.p...ghlight=dither

[steve65]

I saw that but what I was going for mainly was trying to get my form to go from one color to another. All the example that I could find readily at hand went from black to some color mostly blue.

Steve