installed RMagick 2.13.1 on Windows with Ruby v1.9.x

1. Install DevKit : https://github.com/oneclick/rubyinstaller/wiki/Development-Kit .
   
2. Install ImageMagick 6.6.x with windows installer with headers.
   NOTE:
   -Do not install ImageMagick in a path which has spaces in it.
   The default path C:/Program Files/... will not work.
   Install it at a simpler path.
   -- Remove any older installations of ImageMagick and RMagick

3. Set the paths in Environment Variables:

   set DFImageMagick environment variable to where ImageMagick is installed
   set PATH=%DFImageMagick%;%PATH% (if you don't already have it in PATH)
   set CPATH=%DFImageMagick%\include;%CPATH%
   set LIBRARY_PATH=%DFImageMagick%\lib;%LIBRARY_PATH%

4. Install RMagick gem : gem install rmagick
   This should say, Temporarily enhancing PATH to include DevKit... Building native extensions. This could take a while... After some time, Successfully installed rmagick 2.13.1

5. Verify installation:

   A. convert -version
   this should give the ImageMagick installation version
   B. gem list --local should list rmagick 2.13.1
   Alternative: in irb, try
   require 'rmagick'
   it should return 'true'

 

ref:

http://www.ruby-forum.com/topic/204353#new

http://www.waydotnet.com/blog/2010/02/rmagick-on-ruby-1-9-1-i386-mingw32-work-d/# link text