I am using Homebrew v0.9.5 on my Mac OS X version 10.9.4
When I run the command: `brew install imagemagick, this error occurred.
$ brew install imagemagi
For me it was upgrading to El Capitan. I found the simplest solution was to force remove homebrew:
sudo ruby -e "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/master/uninstall)"
then to re-install it:
sudo /usr/bin/ruby -e "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/master/install)"
then install imageMajick:
brew install ImageMagick
Depending on your setup you may not want to sudo. For me, its fine. Enjoy a snack while you manipulate images.