#! /usr/bin/zsh
if [ $# -ne 3 -o "$1" = "--help" ]; then
  echo
  echo 'Usage: virtualtex [--help | <texture name> <tile size> <tile format>]'
  echo 
  echo
  echo The shell script \'virtualtex\' is a tool for Celestia \> 1.3.0 
  echo that supports \'virtual textures\'. 
  echo
  echo The script generates the required tiles tx_i_j of \
       desired \(square\) size,  
  echo \<tile size\>, in a specified format, \<tile format\> = \
       png, tga, jpg,..., 
  echo from an input texture, \<texture name\>, in any popular graphics format.
  echo
  echo Besides Linux/Unix, the script also runs in a current Cygwin \
       installation 
  echo under Windows, \( http://www.cygwin.com \). If the z-shell \(\'zsh\'\) \
       is unavailable,
  echo it also may be executed with the \'bash\' shell, by replacing \
       \#\! /usr/bin/zsh by
  echo \#\! /bin/bash in the first line.
  echo 
  echo The script assumes that a recent version of the ImageMagick package 
  echo \( http://www.ImageMagick.org \) is installed \
       \(either under Unix/Linux or Windows\). 
  echo The utilities \'convert\' and \'identify\' of that package are used.
  echo
  echo Author: Dr. Fridger Schrempp, fridger.schrempp@desy.de
  echo Version: 1.01, 08/13/03
  echo  
else
texturewidth=`/usr/bin/identify $1|cut -d " " -f 3|cut -d x -f 1`
((textureheight = texturewidth/2))
tilesize=$2
tileformat="$3"
echo
echo "Texture size = " $texturewidth "x" $textureheight "tilesize = " $tilesize
echo "Number of tiles =" $(( texturewidth/tilesize * textureheight/tilesize )) 
echo "Image format of tiles:" $tileformat 
echo
echo "Tile: " 
echo
j=0

while (( j * tilesize + tilesize <=  textureheight )); do 
    ((offy = j * tilesize))
    i=0
    while (( i * tilesize + tilesize <= texturewidth )); do 
        ((offx = i * tilesize))
        echo "tx_"${i}"_"${j}":  x-offset:" $offx "y-offset:" $offy
        /usr/bin/convert -crop ${tilesize}x${tilesize}+${offx}+${offy} $1 tx_${i}_${j}.$tileformat
        ((i++))
    done
    ((j++)) 
done
fi