the area threshold to cause re-initialize

delta, in the code, it compares (size_{i}-size_{i-delta})/size_{i-delta}

the aperture size for edge blur

prune the area which bigger than max_area

for color image, the evolution steps

prune the area have simliar size to its children

prune the area which smaller than min_area

trace back to cut off mser with diversity < min_diversity

ignore too small margin