breduce reads a portable bitmap as input, reduces it by a factor of
1/N, and produces a portable bitmap as output.
This program is similar to pbmreduce(4),
but is specialized for Document Image Processing.
Black pixels have priority over white pixels on the reduction
process. Consequently, thin black lines are kept continuous on
the image, while thin white lines may be broken.
If the string "-" is passed instead of
in_file, breduce reads image from standard input.
If the output file
out_file is not specified,
breduce writes image to standard output.