#! /usr/bin/zsh
if [ $# -lt 3 -o "$1" = "--help" ]; then
  echo
  echo 'Usage: virtualtex [--help | <texture name> <tile size> <tile format>] [e|E|w|W]'
  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 The optional 4th argument e\|E\|w\|W is for the case of tiling  
  echo square /e/astern \| /w/estern halfes of the full texture separately!
  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 You may increase the pixel cache size \$maxmem from the 80 MB default
  echo value to e.g. 80\% of your RAM size within the script with an editor. 
  echo This will speed up the performance of \'virtualtex\' considerably. 
  echo
  echo On a PIII/512MB RAM the tiling of a 16k x 8k texture into 
  echo 32 \(2k x 2k\) tiles now only takes 15 minutes with a Linux OS!
  echo
  echo Author: Dr. Fridger Schrempp, fridger.schrempp@desy.de
  echo Version: 1.03, 08/16/03
  echo  
else
maxmem=80
texturesize=`identify $1|cut -d " " -f 3`
texturewidth=`echo $texturesize|cut -d x -f 1`
textureheight=`echo $texturesize|cut -d x -f 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

convert -cache $maxmem -crop ${tilesize}x${tilesize} $1 out%d.$tileformat

j=0

while (( j * tilesize + tilesize <=  textureheight )); do 
    ((offy = j * tilesize))
    if [ $# -eq 4 ]; then
	if [ "$4" = "e" -o "$4" = "E" ]; then
	    ioff=$(( texturewidth/tilesize ))
	elif [ "$4" = "w" -o "$4" = "W" ]; then
	    ioff=0
        else
            echo 
            echo "*** Incorrect 4th parameter! ***" 
            echo
            return
        fi
    fi
    i=0
    while (( i * tilesize + tilesize <= texturewidth )); do 
        ((offx = i * tilesize))
        echo "tx_"$((i + ioff))"_"${j}":  x-offset:" $((offx + ioff * tilesize)) "y-offset:" $offy
    mv out$((i+ ((texturewidth/tilesize)) * j)).$tileformat tx_$((i + ioff))_${j}.$tileformat
        ((i++))
    done
    ((j++)) 
done
fi