Well this the setup for the solution: I attached a colormath node between the displacement map and the displacement value. In the colormath node I subtracted a grey value from the original bitmap, I picked the greycolor with the eyedropper from the original bitmap so the result for the gray region of the bitmap will be black, and the white dot will have a grey value; but what about the black dot? You can't negative colors can't you? Well in fact you can, only it isn't visible: we're used to calcualte with positive colorvalues where white is 255,255,255 and black is 0,0,0 and blacker than black shouldn't be possible But with colormaths it is, the result is a map with negative values but because the computer don't know how display them, (and your eye can't see it either) it is displayed as black, and the result works with the displacement value: See the resullt in the next post.

-How can you improve things when you don't make mistakes?