#!/bin/sh


# Create the template Gnuplot command file
cat > sinc.$$.gnuplot << EOF
#!/opt/local/bin/gnuplot
#!/usr/local/bin/gnuplot
#!/usr/bin/gnuplot
set isosamples 20,20
set hidden3d
set samples 12345
set terminal gif transparent size 640,480 xffffff
set output "OUTFILE"
set view 45,30
set nokey
set noxtics
set noytics
set noztics
set noborder
splot [-15:15] [-15:15] [-2:2] sin(sqrt(x*x+y*y)-000)/sqrt(x*x+y*y)
#pause -1 "press return"
EOF


two_pi='8*a(1)'
phase=0
phase_index=0
phase_num=15
test=1

while expr $phase_index \< $phase_num > /dev/null
do
  phase=`echo 'scale=40 ;' $two_pi '*' $phase_index.0 '/' $phase_num.0 | bc -l`
  if expr $phase_index \< 10 > /dev/null ; then
    phase_index=000${phase_index}
  elif expr $phase_index \< 100 > /dev/null ; then
    phase_index=00${phase_index}
  elif expr $phase_index \< 1000 > /dev/null ; then
    phase_index=0${phase_index}
  fi

  outfile="sinx-$phase_index.gif"

  echo "phase $phase outfile $outfile"

  cat sinc.$$.gnuplot              \
    | sed -e "s/000/$phase/"       \
    | sed -e "s/OUTFILE/$outfile/" \
    > sinc.$$.gp
  chmod a+x sinc.$$.gp
  ./sinc.$$.gp
  phase_index=`expr $phase_index + 1`
done

rm sinc.$$.gp
rm sinc.$$.gnuplot

for gif_file in sinx-[0-9][0-9][0-9][0-9].gif ; do
  small_pnm_file=`echo $gif_file | sed -e 's/\.gif$/-small.pnm/'`
  small_gif_file=`echo $gif_file | sed -e 's/\.gif$/-small.gif/'`

  # The reason for rendering a larger image then shrinking resolution
  # is to antialias lines.  In order to do this correctly, the line
  # width should be 1/scale where scale is the reduction factor.
  # Unfortunately, gnuplot does not correctly implement linewidths for
  # the "gif" terminal type.  We can therefore not allow 'scale' to be
  # too large, otherwise the lines become too faint to be visible.

  giftopnm $gif_file  \
    | pnmcrop -left   \
    | pnmcrop -right  \
    | pnmscale 0.50   \
    > $small_pnm_file
  pnm_info=`pnmfile $small_pnm_file`
  width=`echo $pnm_info | cut -d, -f2 | cut -db -f1`
  height=`echo $pnm_info | cut -dy -f2 | cut -dm -f1`
  pnmcut 0 52 $width 130 $small_pnm_file       \
    | ppmquant 16                                \
    | ppmtogif -sort                             \
    > $small_gif_file
  rm $small_pnm_file
done

rm sinx-[0-9][0-9][0-9][0-9].gif
echo whirlgif -time 4 -loop 0 -o sinx-movie.gif sinx-[0-9][0-9][0-9][0-9]-small.gif