OpenCV 4.X for Android built with cmake on Linux

Android/Java
1

Hi,

I need help building .so files and header files for:

  • arm64-v8a
  • armeabi-v7a
  • x86
  • x86_64

I am interested in any 4.X version which works.

I tried with 4.0.1, 4.5.3, 4.5.2 releases from Git.

    cmake \
        -D CMAKE_TOOLCHAIN_FILE=${ANDROID_NDK_HOME_21}/build/cmake/android.toolchain.cmake \
        -D OPENCV_EXTRA_MODULES_PATH=$SOURCE/opencv/opencv_contrib/modules/ \
        -D BUILD_SHARED_LIBS=ON \
        -D BUILD_TESTS=OFF \
        -D BUILD_PERF_TESTS=OFF \
        -D ANDROID_STL=c++_static \
        -D BUILD_ANDROID_EXAMPLES=OFF \
        -D BUILD_ANDROID_PROJECTS=OFF \
        -D BUILD_JAVA=OFF \
        -D WITH_QT=OFF \
        -D ANDROID_ABI=$ARCH \
        -D ANDROID_NATIVE_API_LEVEL=$ANDROID_VERSION \
        -D CMAKE_BUILD_TYPE=Release \
        -D 3P_LIBRARY_OUTPUT_PATH=$ROOT/output/$OUTARCH/lib/ \
        -D CMAKE_INSTALL_PREFIX:PATH=$ROOT/output/$OUTARCH/lib/ \
        ..

I always get an error that -- Configuring incomplete, errors occurred!

Some of the errors from CMakeError.log:

cpp:21:25: error: use of undeclared identifier 'vcvt_f16_f32'
    float16x4_t v_dst = vcvt_f16_f32(v_src);

CheckIncludeFile.c:1:10: fatal error: 'io.h' file not found

Can somebody please give me some directions?

2

UPDATE: I am able to build without EXTRA MODULES.

1 Like
3

the extra modules (contrib) can be a hassle. if you have trouble with specific modules (in the master branch), and need that resolved, feel free to open an issue on github.

4

related topic (maybe disabling the vfp3 cpu extension helps)

5

I managed to build it with this:

 cmake \
        -D CMAKE_TOOLCHAIN_FILE=${ANDROID_NDK_HOME_21}/build/cmake/android.toolchain.cmake \
        -D ANDROID_NATIVE_API_LEVEL=$ANDROID_VERSION \
        -D BUILD_SHARED_LIBS=ON \
        -D BUILD_TESTS=OFF \
        -D BUILD_PERF_TESTS=OFF \
        -D BUILD_ANDROID_EXAMPLES=OFF \
        -D BUILD_ANDROID_PROJECTS=OFF \
        -D BUILD_JAVA=OFF \
        -D WITH_QT=OFF \
        -D WITH_CAROTENE=ON \
        -D WITH_OPENCL=ON \
        -D WITH_OPENGL=ON \
        -D ANDROID_ABI=$ARCH \
        -D CMAKE_BUILD_TYPE=Release \
        -D 3P_LIBRARY_OUTPUT_PATH=$ROOT/output/$OUTARCH/lib/ \
        -D CMAKE_INSTALL_PREFIX:PATH=$ROOT/output/$OUTARCH/lib/ \
        ..

But there is another error, perhaps not related to OpenCV.
When I try building gomobile with gocv I get this:

# gocv.io/x/gocv
ld: error: undefined symbol: cv::dnn::dnn4_v20210608::readNet(std::__ndk1::basic_string<char, std::__ndk1::char_traits<char>, std::__ndk1::allocator<char> > const&, std::__ndk1::basic_string<char, std::__ndk1::char_traits<char>, std::__ndk1::allocator<char> > const&, std::__ndk1::basic_string<char, std::__ndk1::char_traits<char>, std::__ndk1::allocator<char> > const&)
>>> referenced by dnn.cpp:4
>>>               $WORK/b180/_x021.o:(Net_ReadNet)

ld: error: undefined symbol: cv::dnn::dnn4_v20210608::readNet(std::__ndk1::basic_string<char, std::__ndk1::char_traits<char>, std::__ndk1::allocator<char> > const&, std::__ndk1::vector<unsigned char, std::__ndk1::allocator<unsigned char> > const&, std::__ndk1::vector<unsigned char, std::__ndk1::allocator<unsigned char> > const&)
>>> referenced by dnn.cpp:11
>>>               $WORK/b180/_x021.o:(Net_ReadNetBytes)
6

waay off chartered territory ;(
(noone kows, noone can help …)

what is that chimera ? you seem to mix STL’s here.
your app has to link against the same stl, your libs were build with

7

Solution is to build OpenCV 4.5.3 with NDK23.

This simply works…

 cmake \
        -D CMAKE_TOOLCHAIN_FILE=${ANDROID_NDK_HOME}/build/cmake/android.toolchain.cmake \
        -D ANDROID_NATIVE_API_LEVEL=$ANDROID_VERSION \
        -D BUILD_SHARED_LIBS=ON \
        -D BUILD_TESTS=OFF \
        -D ANDROID_STL=c++_shared \
        -D ENABLE_CXX11=ON \
        -D BUILD_PERF_TESTS=OFF \
        -D BUILD_ANDROID_EXAMPLES=OFF \
        -D BUILD_ANDROID_PROJECTS=OFF \
        -D BUILD_JAVA=OFF \
        -D BUILD_OPENCV_PYTHON=NO \
        -D BUILD_OPENCV_PYTHON2=NO \
        -D BUILD_OPENCV_PYTHON3=NO \
        -D WITH_QT=OFF \
        -D WITH_CAROTENE=ON \
        -D WITH_OPENCL=ON \
        -D WITH_OPENGL=ON \
        -D ANDROID_ABI=$ARCH \
        -D CMAKE_BUILD_TYPE=Release \
        -D 3P_LIBRARY_OUTPUT_PATH=$ROOT/output/$OUTARCH/lib/ \
        -D CMAKE_INSTALL_PREFIX:PATH=$ROOT/output/$OUTARCH/lib/ \
        ..