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OpenCV 3.2.0 prebuilts for Android with LLVM C++ runtime

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opencvandroid-libraryprebuilt-libraries

OpenCV 3.2.0 Prebuilts for Android with LLVM C++ Runtime

Release Build Details

CMake Configuration

  • CMake settings:
ANDROID_TOOLCHAIN_FILE=/home/dev/workspace/dev-tools/Android/Sdk/ndk/21.1.6352462/build/cmake/android.toolchain.cmake
ANDROID_NDK_PATH=/home/dev/workspace/dev-tools/Android/Sdk/ndk/21.1.6352462
# Sources retrieved from https://github.com/opencv/opencv/archive/3.2.0.zip
OPENCV_CMAKEFILE_PATH=/home/dev/workspace/repositories/opencv-3.2.0/opencv-3.2.0
# Set to android-29 and android-25
ANDROID_API_LEVEL=android-29
OPENCV_INSTALL_PATH=/home/dev/workspace/repositories/opencv-3.2.0-android-prebuilts.git/opencv-3.2.0-${ANDROID_API_LEVEL}-arm64-v8a/release
  • CMake command:
# From /home/dev/workspace/repositories/opencv-3.2.0-android-prebuilts.git/opencv-3.2.0-${ANDROID_API_LEVEL}-arm64-v8a/release
cmake ${OPENCV_CMAKEFILE_PATH} -DCMAKE_TOOLCHAIN_FILE=${ANDROID_TOOLCHAIN_FILE} -DANDROID_NDK=${ANDROID_NDK_PATH} -DANDROID_NATIVE_API_LEVEL=${ANDROID_API_LEVEL} -DBUILD_JAVA=OFF -DBUILD_ANDROID_EXAMPLES=ON -DBUILD_ANDROID_PROJECTS=ON -DANDROID_STL=c++_static -DBUILD_SHARED_LIBS=OFF -DCMAKE_INSTALL_PREFIX:PATH=${OPENCV_INSTALL_PATH} -DANDROID_ABI=arm64-v8a -DOPENCV_FP16_DISABLE=ON -DCMAKE_BUILD_TYPE=Release

Debug Build Details

CMake Configuration

  • CMake settings:
ANDROID_TOOLCHAIN_FILE=/home/dev/workspace/dev-tools/Android/Sdk/ndk/21.1.6352462/build/cmake/android.toolchain.cmake
ANDROID_NDK_PATH=/home/dev/workspace/dev-tools/Android/Sdk/ndk/21.1.6352462
# Sources retrieved from https://github.com/opencv/opencv/archive/3.2.0.zip
OPENCV_CMAKEFILE_PATH=/home/dev/workspace/repositories/opencv-3.2.0/opencv-3.2.0
# Set to android-29 and android-25
ANDROID_API_LEVEL=android-29
OPENCV_INSTALL_PATH=/home/dev/workspace/repositories/opencv-3.2.0-android-prebuilts.git/opencv-3.2.0-${ANDROID_API_LEVEL}-arm64-v8a/debug
  • CMake command:
# From /home/dev/workspace/repositories/opencv-3.2.0-android-prebuilts.git/opencv-3.2.0-android-${ANDROID_API_LEVEL}-arm64-v8a/debug
cmake ${OPENCV_CMAKEFILE_PATH} -DCMAKE_TOOLCHAIN_FILE=${ANDROID_TOOLCHAIN_FILE} -DANDROID_NDK=${ANDROID_NDK_PATH} -DANDROID_NATIVE_API_LEVEL=${ANDROID_API_LEVEL} -DBUILD_JAVA=OFF -DBUILD_ANDROID_EXAMPLES=ON -DBUILD_ANDROID_PROJECTS=ON -DANDROID_STL=c++_static -DBUILD_SHARED_LIBS=OFF -DCMAKE_INSTALL_PREFIX:PATH=${OPENCV_INSTALL_PATH} -DANDROID_ABI=arm64-v8a -DOPENCV_FP16_DISABLE=ON -DCMAKE_BUILD_TYPE=Debug

Notes

  • The installation prefix has been explicitely configured for supporting CMake commands such as 'find_package', 'find_program', 'find_library', 'find_path', and 'find_file' in any linked Android projects.
  • FP16 compiler support has been disabled.
    Why? (click to expand)When FP16 support is enabled, CMake logs indicates that the test 'CXX_HAS_MFPU_NEON' is performed and validated, the test 'C_HAS_MFPU_NEON' is performed and validated and the check file 'cmake/checks/fp16.cpp' is ignored. And the libraries and example applications are not successfully built (CMake configuration logs and compilation error logs). From my investigation, it appears that some progress on FP16 compiler support for OpenCV has been integrated (reviewed and merged) following the release 3.2.0. This merge from June 21 is the latest work on this matter, a comment from @alalek introduces some previous pull requests. More details available on a related discussion thread on StackOverflow.
  • The command argument "-DANDROID_SDK_TARGET" is not required if OpenCV Java API and samples are not generated.

How to link OpenCV libraries with the Android Studio project?

  • Add OpenCV include directories and libraries in the CMakeLists.txt file located in the Android project 'app' module folder.
SET( BUILD_TYPE release )

SET( OpenCV_LIB_DIR
    /home/dev/workspace/repositories/opencv-3.2.0-android-prebuilts.git/opencv-3.2.0-android-29-arm64-v8a/${BUILD_TYPE} )

# Retrieve OpenCV_INCLUDE_DIRS and OpenCV_LIBS variables from OpenCVConfig.cmake
FIND_PACKAGE( OpenCV REQUIRED )

MESSAGE( STATUS "Configured OpenCV include directories: ${OpenCV_INCLUDE_DIRS}" )

INCLUDE_DIRECTORIES( ${OpenCV_INCLUDE_DIRS} )

MESSAGE( STATUS "Configured OpenCV libraries: ${OpenCV_LIBS}" )

TARGET_LINK_LIBRARIES( # ...
    # ...
    ${OpenCV_LIBS} )

Troubleshoots

(A) If the OpenCV folder has been moved to another directory and the package configuration file is not found (click to expand)
  • Option 1: Re-edit configured OpenCV_INCLUDE_DIRS variable in OpenCVConfig.cmake.
  • Option 2: Add OpenCV include directories and libraries in the CMakeLists.txt file manually.
SET( BUILD_TYPE release )

SET( OpenCV_ROOT_DIR /home/dev/workspace/repositories/opencv-3.2.0-android-prebuilts.git/ )

SET( OpenCV_LIB_DIR
    ${OpenCV_ROOT_DIR}/opencv-3.2.0-android-29-arm64-v8a/${BUILD_TYPE}/lib/arm64-v8a )

SET( OpenCV_INCLUDE_DIRS 
    ${OpenCV_ROOT_DIR}/opencv-3.2.0-android-29-arm64-v8a/${BUILD_TYPE} 
    ${OpenCV_ROOT_DIR}/opencv-3.2.0/include 
    ${OpenCV_ROOT_DIR}/opencv-3.2.0/include/opencv 
    ${OpenCV_ROOT_DIR}/opencv-3.2.0/modules/core/include 
    ${OpenCV_ROOT_DIR}/opencv-3.2.0/modules/flann/include 
    ${OpenCV_ROOT_DIR}/opencv-3.2.0/modules/imgproc/include 
    ${OpenCV_ROOT_DIR}/opencv-3.2.0/modules/ml/include
    ${OpenCV_ROOT_DIR}/opencv-3.2.0/modules/photo/include 
    ${OpenCV_ROOT_DIR}/opencv-3.2.0/modules/video/include 
    ${OpenCV_ROOT_DIR}/opencv-3.2.0/modules/imgcodecs/include
    ${OpenCV_ROOT_DIR}/opencv-3.2.0/modules/shape/include 
    ${OpenCV_ROOT_DIR}/opencv-3.2.0/modules/videoio/include 
    ${OpenCV_ROOT_DIR}/opencv-3.2.0/modules/highgui/include 
    ${OpenCV_ROOT_DIR}/opencv-3.2.0/modules/objdetect/include 
    ${OpenCV_ROOT_DIR}/opencv-3.2.0/modules/superres/include 
    ${OpenCV_ROOT_DIR}/opencv-3.2.0/modules/ts/include 
    ${OpenCV_ROOT_DIR}/opencv-3.2.0/modules/features2d/include 
    ${OpenCV_ROOT_DIR}/opencv-3.2.0/modules/calib3d/include 
    ${OpenCV_ROOT_DIR}/opencv-3.2.0/modules/stitching/include 
    ${OpenCV_ROOT_DIR}/opencv-3.2.0/modules/videostab/include )

MESSAGE( STATUS "Configured OpenCV include directories: ${OpenCV_INCLUDE_DIRS}" )

INCLUDE_DIRECTORIES( ${OpenCV_INCLUDE_DIRS} )

TARGET_LINK_LIBRARIES( # ...
    # ...
    # Links OpenCV libraries to the 
    # the target library
    ${OpenCV_LIB_DIR}/libopencv_calib3d.a
    ${OpenCV_LIB_DIR}/libopencv_core.a
    ${OpenCV_LIB_DIR}/libopencv_features2d.a
    ${OpenCV_LIB_DIR}/libopencv_flann.a
    ${OpenCV_LIB_DIR}/libopencv_highgui.a
    ${OpenCV_LIB_DIR}/libopencv_imgcodecs.a
    ${OpenCV_LIB_DIR}/libopencv_imgproc.a
    ${OpenCV_LIB_DIR}/libopencv_ml.a
    ${OpenCV_LIB_DIR}/libopencv_objdetect.a
    ${OpenCV_LIB_DIR}/libopencv_photo.a
    ${OpenCV_LIB_DIR}/libopencv_shape.a
    ${OpenCV_LIB_DIR}/libopencv_stitching.a
    ${OpenCV_LIB_DIR}/libopencv_superres.a
    ${OpenCV_LIB_DIR}/libopencv_video.a
    ${OpenCV_LIB_DIR}/libopencv_videoio.a
    ${OpenCV_LIB_DIR}/libopencv_videostab.a
    ${OpenCV_LIB_DIR}/../../3rdparty/lib/arm64-v8a/libIlmImf.a
    ${OpenCV_LIB_DIR}/../../3rdparty/lib/arm64-v8a/liblibjasper.a
    ${OpenCV_LIB_DIR}/../../3rdparty/lib/arm64-v8a/liblibjpeg.a
    ${OpenCV_LIB_DIR}/../../3rdparty/lib/arm64-v8a/liblibpng.a
    ${OpenCV_LIB_DIR}/../../3rdparty/lib/arm64-v8a/liblibtiff.a
    ${OpenCV_LIB_DIR}/../../3rdparty/lib/arm64-v8a/liblibwebp.a
    ${OpenCV_LIB_DIR}/../../3rdparty/lib/arm64-v8a/libtegra_hal.a )

(B) If OpenCV_FOUND variable is founded but is set to 'FALSE'
Set the Android project minimum API level to the configured 'ANDROID_API_LEVEL' value.

(C) If 'zlib' functions such as 'gzopen' are undefined
Add the LDFLAG '-lz' when linking the OpenCV project.

Useful Reading List

  1. sisik.eu: Compiling and Using OpenCV on Android from C++ (Without OpenCVManager)

  2. discuz-android: Build OpenCV for Android with LLVM C++ Runtime

  3. amritamaz.net: Useful Cmake Flags to Turn On and Off in Your OpenCV install

About

OpenCV 3.2.0 prebuilts for Android with LLVM C++ runtime

opencvandroid-libraryprebuilt-libraries

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