script to automate the sprite image generation using image magick and pngcrush

sprite_gen.sh

mkdir revised;
for file in *.png; do
  filename=${file%.*}
  ext=${file#*.}
  mogrify -resize 128x128 -density 72 -units PixelsPerInch -write revised/$filename.128.$ext $file;
  mogrify -resize 64x64   -density 72 -units PixelsPerInch -write revised/$filename.64.$ext  $file;
  mogrify -resize 32x32   -density 72 -units PixelsPerInch -write revised/$filename.32.$ext  $file;
done

montage revised/*.png -geometry +2+2 -background 'rgba(0,0,0,0)' sprites.png

pngcrush sprites.png sprites-optimized.png;