Original source: https://github.com/moyogo/legacy-homebrew/blob/02529f4c80f0daf41c834422ea5a22dd7b8cca21/Library/Formula/imagemagick.rb
Use Ruby version < 2.3. Otherwise you'll get undefined method 'undent' for #<String:0x00007fb026898518>
brew install https://gist.github.com/shev-vadim-net/ecf443abc01c42f4196c5ade675a8714/raw/784132e61a6d62c1b34b8a879e01159c3497e5a1/imagemagick.rb