#! /bin/bash
# Last edited on 2003-02-05 02:54:12 by stolfi

usage="${0##*/} SCALE EXPANSION"

# Reads a PGM image containing a binary mask from standard input. Magnifies it 
# by the given SCALE factor, by smooth interpolation, and thresholds it
# at the 0.5 level. Then expands it by the given EXPANSION (which may be 
# negative for contraction).

if [ $# -ne 2 ]; then echo "usage: ${usage}"; exit 1; fi

scale="$1"; shift;
expand="$1"; shift;
      
level=0.25
if [ ${expand} -lt 0 ]; then expand=$(( -expand )); level=0.75; fi
  
pnmscale ${scale} \
  | pgmmedf \
      -window $((2 * scale + 1)) $((2 * scale + 1)) \
      -round -level 0.5 \
  | pgmmedf \
      -window $((2 * expand + 1)) $((2 * expand + 1)) \
      -round -level ${level}

exit 0