ruby-on-rails – 无法安装RMagick 2.13.1.找不到Magick-config

$gem install rmagick
Building native extensions.  This could take a while...
ERROR:  Error installing rmagick:
    ERROR: Failed to build gem native extension.

        /Users/XXXXXXX/.rvm/rubies/ruby-1.9.2-p180/bin/ruby extconf.rb
checking for Ruby version >= 1.8.5... yes
checking for gcc... yes
checking for Magick-config... no
Can't install RMagick 2.13.1. Can't find Magick-config in /Users/XXXXXXX/.rvm/gems/ruby-1.9.2-p180/bin:/Users/XXXXXXX/.rvm/gems/ruby-1.9.2-p180@global/bin:/Users/XXXXXXX/.rvm/rubies/ruby-1.9.2-p180/bin:/Users/XXXXXXX/.rvm/bin:/Users/XXXXXXX/bin:/usr/bin:/bin:/usr/sbin:/sbin:/usr/local/bin:/usr/local/git/bin:/usr/X11/bin

*** 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/XXXXXXX/.rvm/rubies/ruby-1.9.2-p180/bin/ruby


Gem files will remain installed in /Users/XXXXXXX/.rvm/gems/ruby-1.9.2-p180/gems/rmagick-2.13.1 for inspection.
Results logged to /Users/XXXXXXX/.rvm/gems/ruby-1.9.2-p180/gems/rmagick-2.13.1/ext/RMagick/gem_make.out

但是当我这样做：

$locate Magick-config
/opt/local/bin/Magick-config
/opt/local/share/man/man1/Magick-config.1.gz
/opt/local/var/macports/software/ImageMagick/6.6.4-9_0+q16/opt/local/bin/Magick-config
/opt/local/var/macports/software/ImageMagick/6.6.4-9_0+q16/opt/local/share/man/man1/Magick-config.1.gz
/opt/local/var/macports/software/ImageMagick/6.6.5-0_0+q16/opt/local/bin/Magick-config
/opt/local/var/macports/software/ImageMagick/6.6.5-0_0+q16/opt/local/share/man/man1/Magick-config.1.gz

有任何想法吗？