The icons originate from Font-Awesome font ( http://fontawesome.io ) and licensed under the CC BY 4.0 (SVG download) https://fontawesome.com/license/free The PNGs were generated using ```sh for f in *.svg; do rsvg-convert -a -w 128 -h 128 -o `echo $f | sed -e "s,-solid\.svg,.png,"` $f; done for f in *.png; do convert -background none -gravity center -extent 128x128 $f $f; done ```