#!/bin/sh -ex
# Turn white (or another color) into transparent for the given images
# TODO https://safe.duckduckgo.com/?q=imagemagick+color+to+alpha&ia=web https://stackoverflow.com/questions/26408022/imagemagick-color-to-alpha-like-the-gimp/27194202#27194202
case $1 in (-*) color=${1#-};; esac
for arg
do  extension="-transparent.${arg##*.}"
    case $extension in (*jp*g) extension=".png";; esac
    convert "$arg" -transparent ${color:-white} -fuzz 60% "$arg$extension"
done