install rmagick gem in centos

* rpm -Uvh http://rbel.frameos.org/rbel5
* yum install ImageMagick-devel ImageMagick-c++-devel
* gem install rmagick

test:

require 'rubygems'
require 'RMagick'

系统环境：

ruby -v
ruby 1.8.7 (2011-06-30 patchlevel 352) [x86_64-linux]

lsb_release -a
LSB Version:	:core-4.0-amd64:core-4.0-noarch:graphics-4.0-amd64:graphics-4.0-noarch:printing-4.0-amd64:printing-4.0-noarch
Distributor ID:	CentOS
Description:	CentOS release 5.7 (Final)
Release:	5.7
Codename:	Final