Usage: nearblack [--help] [--long-usage] [--help-general]
[-of <output_format>] [--quiet] [-co <NAME>=<VALUE>]...
[-o <output_file>]
[[-white]|[-color <c1,c2,c3...cn>]...]
[-nb <non_black_pixels>] [-near <dist>] [-setalpha] [-setmask]
[-alg floodfill|twopasses]
<input_file>
Note: nearblack --long-usage for full help.