The --force option for the install action just overwrites any existing files on disk if the packages you're trying to install already exist. It doesn't remove files from disk like the uninstall action does.
I'd do the brew uninstall imagemagick first before doing an install. With brew I find the simplest approach is often the best: I want to reinstall something then I should remove it first with uninstall and put it back with install. The homebrew sandboxing does a very good job of making for clean uninstalls from your system.
If you wanted to uninstall it by hand you'd just need to look in /usr/local/bin for any files that linke to ../Cellar/imagemagick and delete those symlinks. Then delete /usr/local/bin/imagemagick and it's gone. You may be left with some dependency packages that also need removal, but the core imagemagick package will have been deleted. To see what imagemagick depends on if you want to do further cleanup run:
$ brew info imagemagick
imagemagick 6.7.1-1
http://www.imagemagick.org
Depends on: jpeg, libtiff, little-cms, jasper
Not installed
Some tools will complain unless the ghostscript fonts are installed to:
/usr/local/share/ghostscript/fonts
http://github.com/mxcl/homebrew/commits/master/Library/Formula/imagemagick.rb
This is very out of date. See the answer below from @Nelson. – Django Reinhardt – 2017-01-21T15:34:26.820
1@DjangoReinhardt in spite of the appearance of
brew reinstallI still think it's objectively better tobrew uninstalland thenbrew installagain. See discussion on @Nelson's answer for why. – Ian C. – 2017-06-02T20:20:47.913awesome! very helpful! thanks! +1 & ✔ – Meltemi – 2011-08-18T21:24:12.337
I can't seem to rebuild (a full rebuild, from the source) a package, have had this trouble for as long as I can remember using brew: https://gist.github.com/hydrostarr/9766139 . What might I be doing wrong, if anything?
– Johnny Utahh – 2014-03-25T16:52:04.510