Maximum Filter Enhanced

I thought I posted this suggestion before but on a search don't see it.

Anyway if you look at my last filter http://www.filterforge.com/filters/9133.html you'll see that I use the Maximum filter as part of a process to generate cracks. The only problem has always been that this filter uses a grid (3x3?) to average the colors so if you push it the shapes eventually become square. What I'd love to see is a way to use a different shape or size grid for averaging.

For example a 6x3 grid (or two 3x3's rendered as a single grid) would result in brick like shapes. Hexagonal, rhomboid, cross, or custom shaped grids could result in many useful effects. Perhaps this could also be used to offer a similar enhanced Minimum filter or others.