Flood Fill to Position point data in FXMap ?

This might help:

An image is connected to Image 0 input of the FX-Map and a Flood fill to position connected to Image 1 input. The idea is to sample the image input at the centre position points of the Flood Fill to Position node, and map them into a grid.

The overall graph looks like this :

The FX Map looks like this - just creating a grid for the output

The colour/luminosity of the bottom quadrant node is driven by this function.

Reading from the left, the function gets the position of each grid square and uses a sample colour to read the value from input 1 (the Flood Fill Map). It uses the red and green elements as X and Y co-ordinates to sample Image 0 (the picture). So for each grid square it is sampling Image 0 not at the centre of the grid square but at the point dictated by the flood fill position node.

I hope that helps explain how you can use it.

Dave