Created attachment 415732 [details, diff] Patch resolving the issue Building of =dev-ros/image_view-1.12.14 fails if dev-ros/stereo_msgs is not installed. (It uses the header DisparityImage.h from dev-ros/stereo_msgs, and stops if it does not exist.) The attached patch fixes the problem.
commit 9df2da6687ad2c29aa50200a7641b0d7c6cb32c4 Author: Alexis Ballier <aballier@gentoo.org> Date: Mon Nov 2 11:32:28 2015 +0100 dev-ros/image_view: Add missing msg deps. Bug #564462. thanks!