resize @2x pngs to @1x iphone images for an entire folder

halfPNGs.sh

function halfPNGs(){
dir=$1
n=0
while read f
do
  # Image name
  i=$(basename "$f")
  if [[ $i == *\@2x\.png ]]; then
    # Height of image
    h=$(sips -g pixelHeight $f)
    # Cut off all but the numbers
    h=${h#*:}
    # Width of image
    w=$(sips -g pixelWidth $f)
    # Cut off all but the numbers
    w=${w#*:}
    # Resize the png and output in the same folder with @2x cut off
    sips -s format png -z $(expr $h / 2) $(expr $w / 2) $f --out ${f%@*}\.png
  fi
done < <(find $dir -iname *.png) # Find all pngs in directory
}

# Example usage
# halfPNGs ~/Desktop