Imagemagick
From Alessandro's Wiki
- create a copy resized inside a subfolder for every 48 64 128 256, of all png's in the directory
for n in 48 64 128 256;do mkdir $n;for a in `ls -1 *.png`;do convert -resize ${n}x${n} "${a}" "${n}/$a";done;done
for n in 48 64 128 256;do mkdir $n;for a in `ls -1 *.png`;do convert -resize ${n}x${n} "${a}" "${n}/$a";done;done
