smart resize using mogrify http://www.smashingmagazine.com/2015/06/25/efficient-image-resizing-with-imagemagick

.bashrc

smartresize() {
	if [ "$3" == "" ] ; then 
		echo "smartresize inputfile.png 300 outputdir/"
	else
		mogrify -path "$3" -filter Triangle -define filter:support=2 -thumbnail "$2" -unsharp 0.25x0.08+8.3+0.045 -dither None -posterize 136 -quality 82 -define jpeg:fancy-upsampling=off -define png:compression-filter=5 -define png:compression-level=9 -define png:compression-strategy=1 -define png:exclude-chunk=all -interlace none -colorspace sRGB "$1"
	fi
}