Install opencv in ubuntu with venv

Notes

1.  use
   
   <span class="pln">echo $VIRTUAL_ENV</span>

   1	<span class="pln">echo $VIRTUAL_ENV</span>

   
   to know the path of your virtualenv directory. cmake will look for this directory. If it is wrong(after you moved the venv folder), you can change the VIRTUAL_ENVpath in ../bin/activate.
2. Install opencv
   1. http://www.pyimagesearch.com/2015/07/20/install-opencv-3-0-and-python-3-4-on-ubuntu/
   2. https://coderwall.com/p/xzvznq/setting-up-opencv-with-python-virtualenvs
   3. https://medium.com/@manuganji/installation-of-opencv-numpy-scipy-inside-a-virtualenv-bf4d82220313
   4. using cmake after source your_venv/bin/activate is the best way to install opncv
   5. cmake parameters can be vary with at least below
      
      cmake -D MAKE_BUILD_TYPE=RELEASE \ -D CMAKE_INSTALL_PREFIX=$VIRTUAL_ENV/local/ \ -D PYTHON_EXECUTABLE=$VIRTUAL_ENV/bin/python \ -D PYTHON_PACKAGES_PATH=$VIRTUAL_ENV/lib/python2.7/site-packages ..

      1 2 3 4

      cmake -D MAKE_BUILD_TYPE=RELEASE \ -D CMAKE_INSTALL_PREFIX=$VIRTUAL_ENV/local/ \ -D PYTHON_EXECUTABLE=$VIRTUAL_ENV/bin/python \ -D PYTHON_PACKAGES_PATH=$VIRTUAL_ENV/lib/python2.7/site-packages ..

   6. mkdir release or mkdir build are the same, they are just folder to contain compiled files under according to cmake parameters