It's another one of those pesky gem installs.
gem install rmagick -v '2.13.1'
Building native extensions. This could take a while...
ERROR: Error installing rmagick:
ERROR: Failed to build gem native extension.
/mike/.rbenv/versions/1.9.3-p392/bin/ruby extconf.rb
checking for Ruby version >= 1.8.5... yes
extconf.rb:128: Use RbConfig instead of obsolete and deprecated Config.
checking for gcc... yes
checking for Magick-config... yes
checking for ImageMagick version >= 6.4.9... yes
checking for HDRI disabled version of ImageMagick... yes
checking for stdint.h... yes
checking for sys/types.h... yes
checking for wand/MagickWand.h... yes
checking for InitializeMagick() in -lMagickCore... no
checking for InitializeMagick() in -lMagick... no
checking for InitializeMagick() in -lMagick++... no
Can't install RMagick 2.13.1. Can't find the ImageMagick library or one of the dependent libraries. Check the mkmf.log file for more detailed information.
*** extconf.rb failed ***
Could not create Makefile due to some reason, probably lack of
necessary libraries and/or headers. Check the mkmf.log file for more
details. You may need configuration options.
Provided configuration options:
--with-opt-dir
--without-opt-dir
--with-opt-include
--without-opt-include=${opt-dir}/include
--with-opt-lib
--without-opt-lib=${opt-dir}/lib
--with-make-prog
--without-make-prog
--srcdir=.
--curdir
--ruby=/mike/.rbenv/versions/1.9.3-p392/bin/ruby
--with-MagickCorelib
--without-MagickCorelib
--with-Magicklib
--without-Magicklib
--with-Magick++lib
--without-Magick++lib
Gem files will remain installed in /mike/.rbenv/versions/1.9.3-p392/lib/ruby/gems/1.9.1/gems/rmagick-2.13.1 for inspection.
Results logged to /mike/.rbenv/versions/1.9.3-p392/lib/ruby/gems/1.9.1/gems/rmagick-2.13.1/ext/RMagick/gem_make.out
Googling the subject will bring up quite a few various approaches, of which none worked for me. I even uninstalled and re-installed ImageMagick with the --vd option.
The solution to this is to simply perform the following (Ref: https://coderwall.com/p/wnomjg)
$ cd /usr/local/Cellar/imagemagick/6.8.0-10/lib
$ ln -s libMagick++-Q16.7.dylib libMagick++.dylib
$ ln -s libMagickCore-Q16.7.dylib libMagickCore.dylib
$ ln -s libMagickWand-Q16.7.dylib libMagickWand.dylib
Let's try it one more time! Notice that I've passed two paths based on ImageMagick's homebrew install as well.
$ PKG_CONFIG_PATH=/usr/local/Cellar/imagemagick/6.8.0-10/lib/pkgconfig
C_INCLUDE_PATH=/usr/local/Cellar/imagemagick/6.8.0-10/include/ImageMagick gem install rmagick -v '2.13.1'
Building native extensions. This could take a while...
Successfully installed rmagick-2.13.1
1 gem installed
Installing ri documentation for rmagick-2.13.1...
Installing RDoc documentation for rmagick-2.13.1...