Homebrew doctor warning: you have unlinked kegs in your Cellar How do you fix this?

$ brew doctor
...
Warning: You have unlinked kegs in your Cellar
Leaving kegs unlinked can lead to build-trouble and cause brews that depend on
those kegs to fail to run properly once built.

    imagemagick
    jasper
    libtiff
    little-cms
...
Like this, for each unlinked keg:

brew link imagemagick