Blue Noise Dithering · Jan Wedekind
The 1 value in BP with the highest density value DA (tightest cluster) is set to 0 and DA is updated accordingly. Now the 0 value in BP with the lowest density value DA (largest void) is set to 1.
In phase 1 of the dithering algorithm the 1 values of a copy of the seed pattern are removed one by one starting where the density DA is the highest. A copy of the density array DA is updated accordingly. The corresponding positions in the resulting dither array are set to N-1, N-2, ..., 0.
In phase 2 starting with the seed pattern a mask is filled with 1 values where the density DA is the lowest. The density array DA is updated while filling in 1 values. Phase 2 stops when half of the values in the mask are 1. The corresponding positions in the dither array are set to N, N+1, ..., (M * M) / 2 - 1
In phase 3 the density array DA is recomputed using the boolean negated mask from the previous phase (0 becomes 1 and 1 becomes 0). Now the mask is filled with 1 values where the density DA is the highest (clusters of 0s). Phase 3 stops when all the values in the mask are 1. The corresponding positions in the dither array are set to (M * M) / 2, ..., M * M - 1.
