2-d Coarsening operator based on Haar Pyramid
coarse = HCoarsen2d(fine,L)
2-d image on fine grid
integer >= 1. number of dyadic coarsenings
2-d image on coarse grid
Two-by-Two quads of blocks are replaced by single blocks having the average value of the quad. This is repeated through L generations. Starting from data on a grid of n*n points, delivers averages on a coarser grid of n/2^L * n/2^L points.