Hard questions, for the pros out there!

[Chris]

Here is another one:

'This project needs 2 pictureboxes
'Picturebox1 must contain a picture with a lot of white pixels (we're going to use white as transparent color)
Private Declare Function TransparentBlt Lib "msimg32.dll" (ByVal hdc As Long, ByVal x As Long, ByVal y As Long, ByVal nWidth As Long, ByVal nHeight As Long, ByVal hSrcDC As Long, ByVal xSrc As Long, ByVal ySrc As Long, ByVal nSrcWidth As Long, ByVal nSrcHeight As Long, ByVal crTransparent As Long) As Boolean
Private Sub Form_Load()
    Picture1.AutoSize = True
    Picture1.ScaleMode = vbPixels
    Picture2.ScaleMode = vbPixels
End Sub
Private Sub Picture2_Paint()
    'If we don't call DoEvents first, our transparent image will be completely wrong
    DoEvents
    TransparentBlt Picture2.hdc, 0, 0, Picture2.ScaleWidth, Picture2.ScaleHeight, Picture1.hdc, 0, 0, Picture1.ScaleWidth, Picture1.ScaleHeight, vbWhite
End Sub