recurse_image_resize

recurse_image_resize() {
    for f in "$@"; do
        if [ ! -d "$f" ]; then
            echo "recurse_image_resize: '$f' is not a directory"
        fi

        for ff in "$f"/*.png; do
            echo "resizing $ff to half size"
            convert "$ff" -resize 50% "$ff";
        done

        for dir in "$f/*/"; do
            if [ -d "$dir" ]; then  # If there are no subdirectories, glob won't expand. Test just to be sure.
                recurse_image_resize "$dir"
            fi
        done
    done
}