#! /usr/bin/zsh
if [ $# -ne 3 -o "$1" = "--help" ]; then
  echo
  echo 'Usage: virtualtex [--help| <texture name> <tile size> <tile format>]'
  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 <  textureheight )); do 
    ((offy = j * tilesize))
    i=0
    while (( i * 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