[VB6] - about Pointers and Bitmaps

i have 1 nice code for transparent AphaBlend, using Pointers;)
these code gives me results(finally some result after very time trying working with pointers and bitmaps;)):

Code:

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Option Explicit

Private Type SAFEARRAYBOUND
    cElements As Long
    lLbound As Long
End Type

Private Type SAFEARRAY2D
    cDims As Integer
    fFeatures As Integer
    cbElements As Long
    cLocks As Long
    pvData As Long
    Bounds(0 To 1) As SAFEARRAYBOUND
End Type

Private Type BITMAP
    bmType As Long
    bmWidth As Long
    bmHeight As Long
    bmWidthBytes As Long
    bmPlanes As Integer
    bmBitsPixel As Integer
    bmBits As Long
End Type

Private Declare Function VarPtrArray Lib "msvbvm50.dll" Alias "VarPtr" (Ptr() As Any) As Long
Private Declare Sub CopyMemory Lib "kernel32" Alias "RtlMoveMemory" (pDst As Any, pSrc As Any, ByVal ByteLen As Long)
Private Declare Function GetObjectAPI Lib "gdi32" Alias "GetObjectA" (ByVal hObject As Long, ByVal nCount As Long, lpObject As Any) As Long

Private Sub ChangeColors(Source As PictureBox, Destination As PictureBox, Alpha As Byte)
    Dim pic() As Byte
    Dim pic2() As Byte
    Dim sa As SAFEARRAY2D
    Dim bmp As BITMAP
    Dim bmp2 As BITMAP
    Dim r As Long, g As Long, b As Long
    Dim r2 As Long, g2 As Long, b2 As Long
    Dim i As Long, j As Long
    Dim BackColor As Long
    Dim a As Long
    Dim sa2 As SAFEARRAY2D
   
    'Source
    GetObjectAPI Source.Picture, Len(bmp), bmp
   
    With sa
        .cbElements = 1
        .cDims = 2
        .Bounds(0).lLbound = 0
        .Bounds(0).cElements = bmp.bmHeight
        .Bounds(1).lLbound = 0
        .Bounds(1).cElements = bmp.bmWidthBytes
        .pvData = bmp.bmBits
    End With

    CopyMemory ByVal VarPtrArray(pic), VarPtr(sa), 4
   
    'Destination
    GetObjectAPI Destination.Picture, Len(bmp2), bmp2
   
    With sa2
        .cbElements = 1
        .cDims = 2
        .Bounds(0).lLbound = 0
        .Bounds(0).cElements = bmp2.bmHeight
        .Bounds(1).lLbound = 0
        .Bounds(1).cElements = bmp2.bmWidthBytes
        .pvData = bmp2.bmBits
    End With

    CopyMemory ByVal VarPtrArray(pic2), VarPtr(sa2), 4
   
    BackColor = RGB(pic(0 + 2, 0), pic(0 + 1, 0), pic(0, 0))
   
    For i = 0 To UBound(pic, 1) - 3 Step 3
        For j = 0 To UBound(pic, 2)
            r = pic(i + 2, j)
            g = pic(i + 1, j)
            b = pic(i, j)
           
            If RGB(r, g, b) <> BackColor Then
                r2 = pic2(i + 2, j)
                g2 = pic2(i + 1, j)
                b2 = pic2(i, j)
       
                r = (Alpha * (r + 256 - r2)) / 256 + r2 - Alpha
                g = (Alpha * (g + 256 - g2)) / 256 + g2 - Alpha
                b = (Alpha * (b + 256 - b2)) / 256 + b2 - Alpha
            Else
                r = pic2(i + 2, j)
                g = pic2(i + 1, j)
                b = pic2(i, j)
            End If
            If r > 255 Then r = 255
            If r < 0 Then r = 0
            If g > 255 Then g = 255
            If g < 0 Then g = 0
            If b > 255 Then b = 255
            If b < 0 Then b = 0
           
            pic2(i + 2, j) = r
            pic2(i + 1, j) = g
            pic2(i, j) = b
        Next j
    Next i
   
    CopyMemory ByVal VarPtrArray(pic), 0&, 4
    CopyMemory ByVal VarPtrArray(pic2), 0&, 4
   
    Destination.Refresh
End Sub

Private Sub Command1_Click()
    ChangeColors Picture1, Picture2, CByte(Text1.Text)
End Sub

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heres the alpha calculation:

Code:

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FinalPixel = (AlphaValue * (Source + 256 - Destination)) / 256 + Destination - AlphaValue

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the problem is the results:(
because, the pic() position is 0,0, but in pic2() isn't. and seems that the pic() is, maybe, with height, but not with same width:(
can anyone advice me?

see these toturial

and these...