imagemagick on OSX should not be installed with X11 support

Do not link with X11 on OSX!
Unfortunately, by default ImageMagick is linked with X11, but it can also be configured/installed without X11 support, which is better for OSX (no need to package X11 with ImageMagick, and no conflict between OpenGL libraries)
With MacPorts, ImageMagick should be installed with the +no_x11 variant:
sudo port install ImageMagick +no_x11