The first implementation of this property was just plain wrong. Looks
like this property isn't used a lot as I found the issue by reviewing
the code and not because of a specific image.
The test image is a 32x32 mosaic of alternating black and yellow pixels,
it was generated using this code:
Bitdepth 8
RCT 1
Width 32
Height 32
if W-WW-NW+NWW > -300
- Set -1000
- Set 900
