Railsで画像アップローダ作ることがあって、サイズとかもいじりたいからrmagickをいれることにしたときちょっとコケたからメモ。
Gemfile
gem 'carrierwave' # アップローダにはcarrirwaveを使用
gem 'rmagick'
bundle
エラー発生
Gem::Ext::BuildError: ERROR: Failed to build gem native extension.
    /Users/#{username}/.rbenv/versions/2.1.2/bin/ruby extconf.rb 
checking for Ruby version >= 1.8.5... yes
checking for clang... yes
checking for Magick-config... yes
checking for ImageMagick version >= 6.4.9... yes
/usr/local/bin/Magick-config: line 41: pkg-config: command not found
/usr/local/bin/Magick-config: line 47: pkg-config: command not found
/usr/local/bin/Magick-config: line 50: pkg-config: command not found
/usr/local/bin/Magick-config: line 53: pkg-config: command not found
checking for stdint.h... yes
checking for sys/types.h... yes
checking for wand/MagickWand.h... no
Can't install RMagick 0.0.0. Can't find MagickWand.h.
*** 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=/Users/#{username}/.rbenv/versions/2.1.2/bin/ruby
extconf failed, exit code 1
Gem files will remain installed in /Users/#{username}/.rbenv/versions/2.1.2/lib/ruby/gems/2.1.0/gems/rmagick-2.13.3 for inspection.
Results logged to /Users/#{username}/.rbenv/versions/2.1.2/lib/ruby/gems/2.1.0/extensions/x86_64-darwin-14/2.1.0-static/rmagick-2.13.3/gem_make.out
An error occurred while installing rmagick (2.13.3), and Bundler cannot continue.
Make sure that `gem install rmagick -v '2.13.3'` succeeds before bundling.
rmagickいれろと。
gem install rmagick
エラー2
Building native extensions.  This could take a while...
ERROR:  Error installing rmagick:
	ERROR: Failed to build gem native extension.
    /Users/#{username}/.rbenv/versions/2.1.2/bin/ruby extconf.rb
checking for Ruby version >= 1.8.5... yes
checking for clang... yes
checking for Magick-config... yes
checking for ImageMagick version >= 6.4.9... yes
/usr/local/bin/Magick-config: line 41: pkg-config: command not found
/usr/local/bin/Magick-config: line 47: pkg-config: command not found
/usr/local/bin/Magick-config: line 50: pkg-config: command not found
/usr/local/bin/Magick-config: line 53: pkg-config: command not found
checking for stdint.h... yes
checking for sys/types.h... yes
checking for wand/MagickWand.h... no
Can't install RMagick 0.0.0. Can't find MagickWand.h.
*** 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=/Users/#{username}/.rbenv/versions/2.1.2/bin/ruby
extconf failed, exit code 1
Gem files will remain installed in /Users/#{username}/.rbenv/versions/2.1.2/lib/ruby/gems/2.1.0/gems/rmagick-2.13.3 for inspection.
Results logged to /Users/#{username}/.rbenv/versions/2.1.2/lib/ruby/gems/2.1.0/extensions/x86_64-darwin-14/2.1.0-static/rmagick-2.13.3/gem_make.out
pkg-configないよと。。。
入ってるからリンクしなおしたら解決した。
brew unlink pkg-config
brew link pkg-config
これで解決。
gem install rmagick
bundle