#! /bin/bash
# Last edited on 2008-11-23 23:58:32 by stolfi

USAGE="show-pgm-hist {IMG_DIR} {PGM_FILE_1} {PGM_FILE_2}"

imgdir="$1"; shift;
image1="$1"; shift;
image2="$1"; shift;

# Extract the brightness and contrast from file names.
# Assumes file names are "B{BBB}_C{CCC}_{CHANNEL}.pgm"

fld1=( `echo ${image1} | sed -e 's:.*/::' | tr '._' '  '` )
fld2=( `echo ${image2} | sed -e 's:.*/::' | tr '._' '  '` )

br1="${fld1[0]}"; ct1="${fld1[1]}"; ch1="${fld1[2]}"
br2="${fld2[0]}"; ct2="${fld2[1]}"; ch2="${fld2[2]}"
if [[ "/${ch1}" != "/${ch2}" ]]; then
  echo "incompatible channels ${ch1} ${ch2}"; exit 1 
fi

ofile="${imgdir}/hist_${br1}_${ct1}_${br2}_${ct2}_${ch1}.eps"

tmp="/tmp/$$"

i=0
for img in ${image1} ${image2} ; do 
  pgmhist ${imgdir}/${img} \
    | egrep -e '^[ ]*[0-9]' \
    | gawk \
        ' BEGIN{ v = 0;} 
          //{ 
            while ($1 > v) { print v, 0; v++; } 
            print; v = $1;
          } 
        ' \
    > ${tmp}-${i}.dat
  wc -l ${tmp}-${i}.dat
  i=$(( ${i} + 1 ))
done

gnuplot <<EOF
set term postscript eps color "TimesRoman" 24
set output "${ofile}"
set size 2.0,1.5
set xrange [-4:260]
set yrange [-10:20010]
set xtics 16
set xlabel "value"
set ylabel "pixels"
plot \
  "${tmp}-0.dat" using 1:2 title "${br1}_${ct1}" with histeps, \
  "${tmp}-1.dat" using 1:2 title "${br2}_${ct2}" with histeps
quit
EOF

rm -f /tmp/$$*