#!/bin/bash

export tempdir="/tmp/pngcrush-$RANDOM"
mkdir $tempdir

find ./ -name \*.png | sort |\
        xargs -I filename -P 8 \
                sh -c  '
                        f=$(basename "filename" ".png") ;
                        d=$(dirname "filename") ;
                        echo "filename" ;
                        pngcrush -q -brute -rem alla -d $tempdir "filename" ;
                        cp "$tempdir/$f"".png" "$d" '

rm -rf $tempdir