#!/bin/bash
#
# im_graph 'im_function' image_file
#
# Plot a graph the grayscale modification function given on the command line,
# using gnuplot outpuing a GIF image of the adjustment made to a linear
# greyscale image.
#
# See Also
#  im_histogram   draw a mathematical expression as two images
#  im_profile     draw a horizontal profile of a gradient image
#
####
#
# WARNING: Input arguments are NOT tested for correctness.
# This script represents a security risk if used ONLINE.
# I accept no responsiblity for misuse. Use at own risk.
#
# Anthony Thyssen,  29 June 2008
#
PROGNAME=`type $0 | awk '{print $3}'`  # search for executable on path
PROGDIR=`dirname $PROGNAME`            # extract directory of program
PROGNAME=`basename $PROGNAME`          # base name of program
Usage() {                              # output the script comments as docs
  echo >&2 "$PROGNAME:" "$@"
  sed >&2 -n '/^###/q; /^#/!q; s/^#//; s/^ //; 3s/^/Usage: /; 2,$ p' \
          "$PROGDIR/$PROGNAME"
  exit 10;
}

[ $# -eq 0 ] && Usage "Missing im_function"
[ $# -gt 2 ] && Usage "Too many arguments"

im_func=$1
output=$2
[ $# -ne 2 ] && output="show:"  # if not given, display it direct
shift; shift;

#im_func='-sigmoidal-contrast 8x50%'

# Test if gnuplot is new enough
echo "set lmargin at screen 0" | gnuplot >/dev/null 2>&1
if [ $? -ne 0 ]; then
  Error "Gnuplot is too old"
fi

# ---------------------------------------------

# Get the background color to use...
[ -f ./generate_options     ] && source ./generate_options
[ -f ../generate_options    ] && source ../generate_options
[ -f ../../generate_options ] && source ../../generate_options
[ "$page_bg_color" ] || page_bg_color=LightSteelBlue

# Gnuplot of a Level function
# 
# See http://www.cit.griffith.edu.au/~anthony/info/apps/gnuplot.hints
#
#exec 2>/dev/null   # just ignore the SVG error output
( echo "set terminal png size 120,120"
  echo "set lmargin at screen 0"
  echo "set bmargin at screen 0"
  echo "set rmargin at screen 0.99999"
  echo "set tmargin at screen 0.99999"
  echo "set xtics ( 30, 60, 90 ) scale 4"
  echo "set ytics ( 0.25, 0.5, 0.75 ) scale 4"
  echo 'unset key'       # remove function/data plot key
  echo 'unset border'    # remove the drawn border
  echo 'set format ""'   # remove tic mark labeling
  echo 'set xrange [0:119]'
  echo 'set yrange [0:1]'
  echo -n 'plot "-" binary format="%ushort" endian=big'
  echo    '  array=120 using ($1/65536) with lines'
  convert -size 1x120 gradient: -rotate 90 $im_func \
          -depth 16 -endian MSB gray:-
) | gnuplot |
  #convert - -write info: show:; exit  # DEBUGGING
  convert -background $page_bg_color -bordercolor $page_bg_color \
          label:"0                ½                1" \
          -resize 120x -border 1x0 -unsharp 0x.5 \
          -write mpr:label +delete \
          \
          -size 5x120 gradient: +size -rotate 90 -write mpr:gradient \
          $im_func \
          mpr:gradient +swap \
          -bordercolor black -border 1x1 -chop 0x1+0+0 \
          \( - -bordercolor black -border 1x1 \) +insert \
          mpr:label -append \
          \( mpr:label -rotate -90 \) +swap \
          -background $page_bg_color +append \
          -gravity NorthEast -splice 2x2  "$output"
          #-identify show: ; exit

[ -f "$output" ] && chmod 644 "$output"