down samples images from @2x to @1x

downSample.sh

dir=$(pwd)
find "$dir" -name "*@2x.png" | while read image; do

   outfile=$(dirname "$image")/$(basename "$image" @2x.png).png

   if [ "$image" -nt "$outfile" ]; then
       basename "$outfile"

       width=$(sips -g "pixelWidth" "$image" | awk 'FNR>1 {print $2}')
       height=$(sips -g "pixelHeight" "$image" | awk 'FNR>1 {print $2}')
       sips -z $(($height / 2)) $(($width / 2)) "$image" --out "$outfile"

       test "$outfile" -nt "$image" || exit 1
   fi
done