1. A method comprising: accessing a propagation map associated with a watermark from a list having one or more watermarks; defining at least one detection criterion for blocks in the propagation map; generating a flag matrix to identify at least one region; selecting a seed block for initiating the flag matrix from blocks within the propagation map, the seed block being part of the at least one region; determining a signal of the seed block; populating the flag matrix with additional blocks adjacent to the seed block, the additional blocks have the same kind of signal as the seed block; continuing to populate the flag matrix with other blocks that are connected to the seed block through at least the additional blocks, wherein other blocks and any intervening blocks have the same kind of signal as the seed block; assigning the seed block and any blocks in the populating and further populating to a first region, thereby producing the first region for identifying the at least one region; identifying the at least one region of at least one of the blocks contained within the propagation map, wherein the at least one region is grouped responsive to the at least one detection criterion; and producing information of the at least one region.