What is meant with half support for the 16BIT_PIXEL option and HDRI
option is that either by disabling 16BIT_PIXEL or enabling HDRI the
library names change. The ImageMagick port works fine and package
correctly. But ports that depend on ImageMagick might not be able to
find ImageMagick libraries anymore via the port framework.

So please keep that in mind if you need a port that ImageMagick and
you want to change these options.