ImageMagick Installation
Ubuntu machine has default apt-get package manager.
To install imagemagick following packages needs to be installed.
apt-get install imagemagick librmagick-ruby libmagickwand-dev
RMagick gem install
gem install rmagick
If you still facing problems with gem installation, Please look that following packages are installed
on your system.
dpkg -l | grep libmagickcore-dev graphicsmagick-libmagick-dev-compat
If there are no packages installed then try to install then first.
apt-get install libmagickcore-dev graphicsmagick-libmagick-dev-compat
Try to install rmagick gem again. Now it should be installed without any error.
Josh Software 