make error？

[ucas010]

hi,dear
I make according with the codes

git clone --recursive http://github.com/yjxiong/dense_flow
mkdir build && cd build
cmake .. && make -j

but then I got mistake

CMake Error at CMakeLists.txt:18 (find_package):
  By not providing "FindOpenCV.cmake" in CMAKE_MODULE_PATH this project has
  asked CMake to find a package configuration file provided by "OpenCV", but
  CMake did not find one.

  Could not find a package configuration file provided by "OpenCV" with any
  of the following names:

    OpenCVConfig.cmake
    opencv-config.cmake

  Add the installation prefix of "OpenCV" to CMAKE_PREFIX_PATH or set
  "OpenCV_DIR" to a directory containing one of the above files.  If "OpenCV"
  provides a separate development package or SDK, be sure it has been
  installed.


-- Configuring incomplete, errors occurred!
See also "/home/xulm1/xulm1/dense_flow/build/CMakeFiles/CMakeOutput.log".

I have installed opencv-python

>>> import cv2
>>> quit()

should I install OpenCV source codes ??
Or how to solve the problem ?
thx