How to make a Pointillizer effect through vba?

Good day.
I do not even know where to dig ((
I tried to write a macro when this effect is applied - it turned out like this
Dim s1 as shape
Set s1 = ActiveShape.Shapes (1) .Shapes (1) .ConvertToBitmapEx (4, False, True, 30, 1, True, False, 0)

but if you then re-start it - it turns out the usual pixelation - absolutely not what should have happened.
maybe someone came across - tell me where to dig?

Sorry for my English. translated through translator