' Draw on the memory bitmap.
Private Sub DrawOnMemoryBitmap(memory_bitmap As _
    MemoryBitmap)
Dim pixels() As Byte
Dim x As Integer
Dim Y As Integer
Dim R As Single
Dim dR As Single
Dim G As Single
Dim dG As Single
Dim i As Integer

    ' Load the bitmap's data into an array.
    ReDim pixels(1 To 4, _
        1 To memory_bitmap.wid, _
        1 To memory_bitmap.hgt)
    GetDIBits memory_bitmap.hdc, memory_bitmap.hBM, _
        0, memory_bitmap.hgt, pixels(1, 1, 1), _
        memory_bitmap.bitmap_info, DIB_RGB_COLORS

    ' Modify the pixels.
    R = 0
    dR = 255 / memory_bitmap.hgt
    dG = 255 / memory_bitmap.wid
    For Y = 1 To memory_bitmap.hgt
        G = 0
        For x = 1 To memory_bitmap.wid
            pixels(pixB, x, Y) = 255
            pixels(pixR, x, Y) = R
            pixels(pixG, x, Y) = G
            G = G + dG
        Next x
        R = R + dR
    Next Y

    ' Set some pixels halfway down the diagonal.
    For i = 1 To memory_bitmap.hgt \ 2 Step 10
        ' Make this block of pixels green.
        For x = 0 To 10
            For Y = 0 To 10
                pixels(pixR, i + x, i + Y) = 0
                pixels(pixG, i + x, i + Y) = 255
                pixels(pixB, i + x, i + Y) = 0
            Next Y
        Next x
    Next i

    ' Copy the results back into the memory bitmap.
    SetDIBits memory_bitmap.hdc, memory_bitmap.hBM, _
        0, memory_bitmap.hgt, pixels(1, 1, 1), _
        memory_bitmap.bitmap_info, DIB_RGB_COLORS

    ' Draw the on the device context.
    SelectObject memory_bitmap.hdc, _
        GetStockObject(BLACK_PEN)
    MoveToEx memory_bitmap.hdc, 0, 0, ByVal 0&
    LineTo memory_bitmap.hdc, memory_bitmap.wid, _
        memory_bitmap.hgt
    MoveToEx memory_bitmap.hdc, 0, memory_bitmap.hgt, ByVal _
        0&
    LineTo memory_bitmap.hdc, memory_bitmap.wid, 0
End Sub