This is a PPA of OpenCV 3.0 for Ubuntu trusty ported from Debian's experimental OpenCV 3.0 package. Also provide the python3-opencv package.
$ sudo add-apt-repository ppa:orangain/opencv
$ sudo apt-get update
$ sudo apt-get install python3-opencv
$ git clone https://github.com/orangain/opencv-ppa
$ cd opencv-ppa/
$ wget http://http.debian.net/debian/pool/main/o/opencv/opencv_3.0.0+dfsg.orig.tar.xz
$ tar xvf opencv_3.0.0+dfsg.orig.tar.xz -C opencv/ --strip 1
$ cd opencv/
$ debuild -b -rfakeroot -uc -us
$ dch -U -D xenial # Then write release notes in your editor
$ git add . ; git commit ; git tag ubuntu/ppaN
$ debuild -S -sa # GPG key is required
$ dput ppa:orangain/opencv ../opencv_3.0.0+dfsg-1ubuntu1ppaN_source.changes
$ ./docker_run.sh debuild -b -rfakeroot -uc -us
$ ./docker_run.sh dch -U -D xenial # Then write release notes in your editor
$ git add . ; git commit ; git tag ubuntu/xenial-ppaN
$ ./docker_run.sh debuild -S -sa # GPG key is required
$ ./docker_run.sh dput ppa:orangain/opencv ../opencv_3.0.0+dfsg-1ubuntu1ppaN_source.changes
If you see the following error, you should remove opencv dir then run git checkout opencv and tar xvf opencv_3.0.0+dfsg.orig.tar.xz -C opencv/ --strip 1. This will reset the source tree of opencv.
dpkg-source: info: local changes detected, the modified files are:
opencv/cmake/OpenCVDetectPython.cmake
dpkg-source: error: aborting due to unexpected upstream changes, see /tmp/opencv_3.0.0+dfsg-1ubuntu1ppa4.diff.3xNld2
dpkg-source: info: you can integrate the local changes with dpkg-source --commit
dpkg-buildpackage: error: dpkg-source -b opencv gave error exit status 2