Question

I’m using Mac Lion with RVM, homebrew and bundler and the rmagick gem

When I execute the following command:

brew install imagemagick

convert --version

the imagemagick version that is installed is Q16 (16-bit depth) , but I prefer the 8-bit depth version for speed reasons.

what is the correct brew command to achieve this?

Answer 1

I realised homebrew formula’s are just ruby scripts, so searched for the imagemagick formula.

locate imagemagick.rb

So you can see all the available options in the options method in:

/usr/local/Library/Formula/imagemagick.rb 

So in the end, it was just a simple

brew install imagemagick --with-quantum-depth-8

See also homebrew install imagemagick 8 bit version

UPDATE for brew 2

Brew version 2 does not allow additional compile (./configure) settings anymore. You now have to edit the fromula yourself and recompile.

Open and edit the brew formula

brew edit imagemagick

Add the following line under the args = %W[ section

--with-quantum-depth=8

Then install and coile with -s

brew install imagemagick -s

Then test your new installation of ImageMagick with

convert --version

You will see the Q8 on the first line after the version number.

P.S.
if you use rmagick, and just changed your ImageMagick, make sure you gem uninstall rmagick && bundle install