Homebrew

Homebrew is a package manager that allows you to install software. To install Homebrew, follow these Terminal command line instructions:

install homebrew

/usr/bin/ruby -e "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/master/install)"

install graphviz

brew install graphviz

install opencv

brew doctor

brew tap homebrew/science

brew install opencv3 --with-java --with-contrib

lines repeated for copying to clipboard

/usr/bin/ruby -e "$(curl -fsSL https://raw.githubusercontent.com/Homebrew/install/master/install)"
brew install graphviz
brew doctor
brew tap homebrew/science
brew install opencv3 --with-java --with-contrib