#!/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, magick 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
#
size_w=120 size_h=120   # size of the desired gnuplot drawing area
                        # this does not include any borders.
                        # width is also the number of input values given

# gnuplot terminal size (version dependant - Arrgghhhh)
gsize="`expr $size_w + 1`,`expr $size_h + 1`"
grange="`expr $size_w - 1`"    # 0 to $grange values input
# note gnuplot output is +1 desired size and needs to be trimmed.

#exec 2>/dev/null   # just ignore the SVG error output
( echo "set terminal png size $gsize"
  echo "set lmargin at screen 0"
  echo "set bmargin at screen 0"
  echo "set rmargin at screen 0.99999"
  echo "set tmargin at screen 0.99999"
  echo "set xtics ( 30, 60, 90 ) scale 4"
  echo "set ytics ( 0.25, 0.5, 0.75 ) scale 4"
  echo 'unset key'       # remove function/data plot key
  echo 'unset border'    # remove the drawn border
  echo 'set format ""'   # remove tic mark labeling
  echo "set xrange [0:$grange]"
  echo 'set yrange [0:1]'

  # Read image Data in Binary
  echo -n 'plot "-" binary format="%ushort" endian=big'
  echo    '  array='"$size_w"' using ($1/65536) with lines'
  eval magick -size 1x$size_w gradient: -rotate 90 $im_func \
          -depth 16 -endian MSB gray:-

) | gnuplot |
  #magick - -write info:fd:2 miff:- | magick display -; exit  # DEBUGGING
  magick -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 \
          \( - -trim +repage  -bordercolor black -border 1x1 \) +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"