Building OpenCV on MacOSX High Sierra with Python3, QT and contrib

At the time of writing this, I had actually successfully built and installed OpenCV earlier but after havimg upgraded brew packages at some time or other, the version I had built stopped working due to no longer having access to an old version of libhdf5.

I have cloned the OpenCV and OpenCV contrib repos. In this particular case, I also want to go from version 3.4.2 to 3.4.3.

First, make sure we have the necessary dependencies, although I’m not quite sure the below covers everything we need.

brew install eigen ffmpeg harfbuzz hdf5 lapack libpng libsvg libtiff numpy
     openblas openjpg python qt tbb

Now, retrieve and checkout the 3.4.3 branch in the opencv repo

cd opencv
git checkout master
git pull
git checkout 3.4.3
git checkout -b my-3.4.3

Then we do the same thing for contrib

cd ../opencv_contrib
git checkout master
git pull
git checkout 3.4.3
git checkout -b my-3.4.3
cd ../opencv

I have previously setup a virtualenv with pyenv for Python 3.7.0 and pip installed numpy, imutils and pyyaml

pyenv activate opencv

In the opencv repo, if this is not an upgrade

mkdir build
cd build
vim build.sh

where build.sh should contain

PREFIX_MAIN=`pyenv virtualenv-prefix`
PREFIX=`pyenv prefix`
cmake .. \
    -DCMAKE_BUILD_TYPE=RELEASE \
    -DCMAKE_INSTALL_PREFIX="$PREFIX" \
    -DOPENCV_ENABLE_NONFREE=ON \
    -DWITH_OPENGL=ON \
    -DWITH_OPENVX=ON \
    -DWITH_QT=ON \
    -DWITH_OPENCL=ON \
    -DBUILD_PNG=ON \
    -DBUILD_TIFF=ON \
    -DOPENCV_EXTRA_MODULES_PATH=~/src/opencv_root/opencv_contrib/modules \
    -DWITH_1394=OFF \
    -DWITH_AVFOUNDATION=ON \
    -DWITH_QUICKTIME=OFF \
    -DWITH_CUDA=OFF \
    -DBUILD_opencv_python2=OFF \
    -DBUILD_opencv_python3=ON \
    -DPYTHON3_EXECUTABLE="$PREFIX"/bin/python3.7 \
    -DPYTHON3_PACKAGES_PATH="$PREFIX"/lib/python3.7/site-packages \
    -DPYTHON3_LIBRARY="$PREFIX_MAIN"/lib/libpython3.7m.dylib \
    -DPYTHON3_INCLUDE_PATH="$PREFIX_MAIN"/include/python3.7m \
    -DPYTHON3_NUMPY_INCLUDE_DIRS="$PREFIX"/lib/python3.7/site-packages/numpy/core/include
\
    -DINSTALL_C_EXAMPLES=OFF \
    -DINSTALL_PYTHON_EXAMPLES=OFF \
    -DINSTALL_NAME_DIR="${CMAKE_INSTALL_PREFIX}/lib"

Now, better be safe than sorry (external dependencies might have changed since we built last time)

rm CMakeCache.txt
make clean

and then

./build.sh
make install

Test the install by running

$ python
Python 3.7.0 (default, Jul 31 2018, 23:01:49)
[Clang 6.0.1 (tags/RELEASE_601/final)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> import cv2
>>> import numpy as np
>>> cv2.namedWindow("image", cv2.WINDOW_NORMAL)
>>> cv2.imshow("image", np.array([0, 128, 255]))
>>> cv2.waitKey(0)

If the QT window shows up – success!