CMAKE for opencv 3.0 installing don't find python3

Question

I'm trying to install opencv 3.0 on MacOS 10.13 and when I use that instructions:

cmake -D CMAKE_BUILD_TYPE=RELEASE \
    -D CMAKE_INSTALL_PREFIX=/usr/local \
    -D OPENCV_EXTRA_MODULES_PATH=~/opencv_contrib/modules \
    -D PYTHON3_LIBRARY=YYY \
    -D PYTHON3_INCLUDE_DIR=ZZZ \
    -D PYTHON3_EXECUTABLE=$VIRTUAL_ENV/bin/python \
    -D BUILD_opencv_python2=OFF \
    -D BUILD_opencv_python3=ON \
    -D INSTALL_PYTHON_EXAMPLES=ON \
    -D INSTALL_C_EXAMPLES=OFF \
    -D BUILD_EXAMPLES=ON ..

The installation don't find my python 3 compiler and shows me that:

Python 3:
--     Interpreter:                 NO
--     Libraries:                   NO
--     numpy:                       NO (Python3 wrappers can not be generated)
--     packages path:

How may I fix it to find the python 3 compiler? I've installed the python3 using "brew install python3"

you havn't install numpy

Kinght 金
– Kinght 金

2017-10-08 02:46:43 +00:00
Commented Oct 8, 2017 at 2:46 — Kinght 金
– Kinght 金, Commented Oct 8, 2017 at 2:46

svenevs · Accepted Answer · 2017-10-08 02:09:35Z

You probably need to provide full paths. Perhaps the $VIRTUAL_ENV part is your problem? Installing it with a virtualenv python3 (e.g. with numpy) may be a completely different problem altogether though.

-DBUILD_opencv_python3=ON
-DPYTHON3_EXECUTABLE=/full/path/to/bin/python3
-DPYTHON3_LIBRARY=/full/path/to/lib
-DPYTHON3_INCLUDE_DIR=/full/path/to/include
-DBUILD_opencv_python2=OFF

You mentioned OSX with brew, so you may also be missing a slightly arcane path issue here. On my system I have installed python3 with brew, the version I have installed is 3.6.2. So these paths actually need to be

/usr/local/Cellar/python3/3.6.2/Frameworks/Python.framework/Versions/3.6/bin/python3
/usr/local/Cellar/python3/3.6.2/Frameworks/Python.framework/Versions/3.6/lib
/usr/local/Cellar/python3/3.6.2/Frameworks/Python.framework/Versions/3.6/include/

The Frameworks stuff is an OSX specific thing, but the bin/ folder gets symlinked up to /usr/local/Cellar/python3/3.6.2 whereas the others (lib and include) do not

HOWEVER

Why not just use brew to install it? brew info opencv shows opencv.rb, which will use python3. That may be the path of least resistance here ;)

Note that OpenCV is "bottled", which means by default brew will try and install the bottle first. It's generally better to install OpenCV from source (it gets compiled to your specific machine), so you will want to

brew install --build-from-source opencv

Of course this will take significantly longer to install!

Update: you may not have opencv available directly in brew yet, to get it you need to

brew tap homebrew/science
brew install --build-from-source opencv

More information on that and what comes with homebrew/science here.

Julia Aleksandrova · Accepted Answer · 2018-06-04 16:13:47Z

0

I had the same problem as the topic starter, and the way with brew worked for me.

The only thing:

brew install --build-from-source opencv installed opencv for python2

brew install --build-from-source opencv3 worked for python3

answered Jun 4, 2018 at 16:13

Julia Aleksandrova

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