#!/bin/sh
#
# pamstretch-gen - a shell script which acts a little like a general
# 	form of pamstretch, by scaling up with pamstretch then scaling
# 	down with pnmscale.
#
# it also copes with N<1, but then it just uses pnmscale. :-)
#
# by Russell Marks, 1999.
# Contributed to the public domain.

if [ "$1" = "" ]; then
  echo 'usage: pamstretch-gen N [pnmfile]'
  exit 1
fi

tempfile=$(mktemp -t pnmig.XXXXXXXXXX) || exit 1 #219019

if ! cat $2 >$tempfile 2>/dev/null; then
  echo 'pamstretch-gen: error reading file' 1>&2
  exit 1
fi

# we use the width as indication of how much to scale; width and
# height are being scaled equally, so this should be ok.
width=`pnmfile $tempfile 2>/dev/null|cut -d " " -f 3`

if [ "$width" = "" ]; then
  echo 'pamstretch-gen: not a PNM file' 1>&2
  exit 1
fi

# should really use dc for maths, but awk is less painful :-)
target_width=`awk 'BEGIN{printf("%d",'0.5+"$width"*"$1"')}'`

# work out how far we have to scale it up with pnmstretch so that the
# new width is >= the target width.
int_scale=`awk '
BEGIN {
int_scale=1;int_width='"$width"'
while(int_width<'"$target_width"')
  {
  int_scale++
  int_width+='"$width"'
  }
print int_scale
}'`

if [ "$int_scale" -eq 1 ]; then
  pnmscale "$1" $tempfile
else
  pamstretch "$int_scale" $tempfile | pnmscale -xsi "$target_width"
fi

rm -f $tempfile;