Crush All PNGs Starting From Root Directory.

compressallpng.sh

#!/bin/bash

(find . -name "*.png")|while read pngfile
do
  PNG_FILE=$pngfile
  PNG_TMP=$RANDOM.compressallpng.png
  pngcrush -brute $PNG_FILE $PNG_TMP
  mv $PNG_TMP $PNG_FILE
done