Usage: nearblack [--help] [--help-general]
[-of <format>] [-white | [-color <c1>,<c2>,<c3>...<cn>]...]
[-near <dist>] [-nb <non_black_pixels>]
[-setalpha] [-setmask] [-alg twopasses|floodfill]
[-o <outfile>] [-q] [-co <NAME>=<VALUE>]... <infile>