^^&&^^

Edit File: pnminterp-gen

#!/bin/sh
###############################################################################
#                              pamstretch-gen
###############################################################################
# A generalized version of pamstretch that can do non-integer scale factors.
#
# It works by scaling up with pamstretch then scaling down with pamscale.
#
# it also copes with N<1, but then it just uses pamscale. :-)
#
# Formerly named 'pnminterp-gen' and 'pnmstretch-gen'.
#
###############################################################################

# Scan command line arguments

while true ; do
    case "$1" in
        -version|--version )
        pamstretch --version; exit $?;
        ;;
        -p|-pl|-pla|-plai|-plain|--p|--pl|--pla|--plai|--plain )
        plainopt="-plain"
        shift
        ;;
        -q|-qu|-qui|-quie|-quiet|--q|--qu|--qui|--quie|--quiet )
        quietopt="-quiet"
        shift
        ;;
        -verb|-verbo|-verbos|-verbose|--verb|--verbo|--verbos|--verbose )
        verboseopt="-verbose"
        shift
        ;;
        -* )
        echo 'usage: pamstretch-gen N [pnmfile]' 1>&2
        exit 1
        ;;
        * )
        break
        ;;
    esac
done
 
tempfile=$(mktemp "${TMPDIR:-/tmp}/netpbm.XXXXXXXX")
if [ $? -ne 0 -o ! -e $tempfile ]; then
  echo "Could not create temporary file. Exiting." 1>&2
  exit 1
fi
trap 'rm -rf $tempfile' 0 1 3 15

case "$#" in
    0)
    echo "pamstretch-gen: too few arguments" 1>&2
    exit 1
    ;;   
    1 )
    if ! cat > $tempfile; then
    echo "pamstretch-gen: error reading input" 1>&2
    exit 1
    fi
    ;;
    2 )
    if ! cat $2 > $tempfile; then
    echo "pamstretch-gen: error reading file "$2 1>&2
    exit 1
    fi
    ;;
    * )
    echo "pamstretch-gen: misaligned arguments or too many arguments" 1>&2
    exit 1
    ;;
esac

# Calculate pamstretch scale factor (="iscale") and output width and
# height.  Usually "int(scale) + 1" is sufficient for iscale but
# in some exceptional cases adjustment is necessary because of
# "-dropedge".

report=$(pamscale $quietopt -reportonly $1 $tempfile)
if [ $? -ne 0 ]; then
  echo "pamstretch-gen: pamscale -reportonly $1 (file) failed" 1>&2
  exit 1
fi

iscale_width_height=$(echo $report |\
  awk 'NF!=6 || $1<=0 || $2<=0 || $3<=0 || $5<=0 || $6<=0  { exit 1 }
           { if ($3 > 1.0)  { iscale = int($3) + 1;
                              if (iscale * ($1-1) < $5 ||
                                  iscale * ($2-1) < $6 )
                                     ++iscale;            }
             else { iscale = 1 }  # $3 <= 1.0
       }
       { print iscale, "-width="$5, "-height="$6}' )

# Note that $1, $2, ..., $6 here are fields of the input line fed to awk,
# not shell positional parameters.

iscale=${iscale_width_height% -width=* -height=*}
width_height=${iscale_width_height#* }
if [ -n "$verboseopt" ]; then
    echo "pamstretch-gen: rounded scale factor=$iscale $width_height" 1>&2
fi

pamstretch -dropedge $quietopt $iscale $tempfile |\
  pamscale $verboseopt $quietopt $plainopt $width_height

# Copyright (C) 1998,2000 Russell Marks.
# Modifications for "pamscale -reportonly" "pamstretch -dropedge" by
# Akira Urushibata (Jan. 2019)
#
# This program is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2 of the License, or (at
# your option) any later version.
#
# This program is distributed in the hope that it will be useful, but
# WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
# General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program; if not, write to the Free Software
# Foundation, 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.