本段说明链接来源

OpenCV 整套代码是基于 C 和 C++实现的，在 Android 上调用存在两种方式:

Java Native 代码实现
C++ NDK 代码实现

** 其中 Java Native 代码实现是直接通过 Java OpenCV API 编写算法实现部分，相对应的特点在于:**

环境搭建简单:直接引入官方 OpenCV-for-Android 的对应 jar 包即可
代码维护繁琐:由于OpenCV-for-Android 的Java API与C++不完全相同，任何算法的更新都需要重写 => 在存在 Windows、iOS 等多平台更新时比较麻烦
运行效率低:Java 代码会在内部进行 C++翻译，运行时性能损耗较大

** 而直接采用 C++代码导入的方式的特点在于:**

环境搭建复杂:往往需要现自行编译对应的库，再进行NDK、Cmakelists和build.gradle的配置.
代码维护简单:由于直接采用 C++实现算法部分，与其他平台的兼容性极好，能与 Android 程序员分离开发 => 算法升级时替换对应的算法库文件即可.
运行效率高:不存在内部执行时的代码转换问题，性能最好.
总结来看，Java Native 代码实现是爽一时但是后面会不爽很久，对于有时间精力且要求较高的开发任务，强烈建议多花点时间搭建 C++ NDK 方式.

如果自己不从源码编译也可去这里下载,网上很多配置教程都是基于这里下载的 SDK 而写的.如: Android Studio 集成 OpenCV

Python 脚本编译

依赖工具
- CMake > 3.7
- ninja-build
- ccache
- python

安装编译工具

~$ apt-get install ninja-build  ccache
~$ export ANDROID_SDK=/fullpath/Android/Sdk
~$ export ANDROID_NDK=/fullpath/Android/Sdk/android-ndk-r16b

~$ mkdir build
~$ cd build ../opencv-3.4.1/platforms/android/build_sdk.py --no_ccache --extra_module=/fullpath/opencv_contrib-3.4.1/modules --config=ndk-16.config.py  build-ndk ../opencv-3.4.1

使用opencv-3.4.1/platforms/android/build_sdk.py 脚本安装,可以一次编译多种平台的 SDK,相关的一些配置要参照文件ndk-16.config.py.
如果没有出错误的话,build-ndk目录结构如下:

~$ tree build-ndk -L 1
build-ndk
├── build_service_arm64-v8a
├── build_service_armeabi
├── build_service_armeabi-v7a
├── build_service_x86
├── build_service_x86_64
├── o4a
└── OpenCV-android-sdk

7 directories, 0 files

~$ tree build-ndk/OpenCV-android-sdk/ -L 2
build-ndk/OpenCV-android-sdk/
├── apk
│   ├── OpenCV_3.4.1_Manager_3.41_arm64-v8a.apk
│   ├── OpenCV_3.4.1_Manager_3.41_armeabi.apk
│   ├── OpenCV_3.4.1_Manager_3.41_armeabi-v7a.apk
│   ├── OpenCV_3.4.1_Manager_3.41_x86_64.apk
│   ├── OpenCV_3.4.1_Manager_3.41_x86.apk
│   └── readme.txt
├── LICENSE
├── README.android
├── samples
│   ├── 15-puzzle
│   ├── camera-calibration
│   ├── color-blob-detection
│   ├── example-15-puzzle.apk
│   ├── example-camera-calibration.apk
│   ├── example-color-blob-detection.apk
│   ├── example-face-detection.apk
│   ├── example-image-manipulations.apk
│   ├── example-tutorial-1-camerapreview.apk
│   ├── example-tutorial-2-mixedprocessing.apk
│   ├── example-tutorial-3-cameracontrol.apk
│   ├── face-detection
│   ├── image-manipulations
│   ├── tutorial-1-camerapreview
│   ├── tutorial-2-mixedprocessing
│   └── tutorial-3-cameracontrol
└── sdk
    ├── build.gradle
    ├── etc
    ├── java
    └── native

14 directories, 17 files

~$ tree build-ndk/OpenCV-android-sdk/sdk/native -L 2
build-ndk/OpenCV-android-sdk/sdk/native
├── 3rdparty
│   └── libs
├── jni
│   ├── abi-arm64-v8a
│   ├── abi-armeabi
│   ├── abi-armeabi-v7a
│   ├── abi-x86
│   ├── abi-x86_64
│   ├── android.toolchain.cmake
│   ├── include
│   ├── OpenCV-arm64-v8a.mk
│   ├── OpenCV-armeabi.mk
│   ├── OpenCV-armeabi-v7a.mk
│   ├── OpenCVConfig.cmake
│   ├── OpenCVConfig-version.cmake
│   ├── OpenCV.mk
│   ├── OpenCV-x86_64.mk
│   └── OpenCV-x86.mk
├── libs
│   ├── arm64-v8a
│   ├── armeabi
│   ├── armeabi-v7a
│   ├── x86
│   └── x86_64
└── staticlibs
    ├── arm64-v8a
    ├── armeabi
    ├── armeabi-v7a
    ├── x86
    └── x86_64

21 directories, 9 files

CMake 编译方式

编译环境

android-ndk-r14b
tools_r25.2.5
这里可能要注意, 本次编译测试必須使用**[tools_r25.2.5]**
建议使用**[tools_r25.2.5]**测试编译,不然有可能会出现如下错误

--     SDK target:  android_sdk_target-NOTFOUND

[...]
The "android" command is deprecated.
For manual SDK, AVD, and project management, please use Android Studio.
For command-line tools, use tools/bin/sdkmanager and tools/bin/avdmanager
*************************************************************************
Invalid or unsupported command "--silent create lib-project --path /fullpath/opencv-3.4.1/build-android/android_sdk --target android_sdk_target-NOTFOUND --name OpenCV --package org.opencv"
[...]

CMake 单独编译参数

~$ cd /fullpath/Android/Sdk
~$ ln -svf tools_r25.2.5 tools
~$ ln -svf android-ndk-r14b ndk-bundle
~$ export ANDROID_NDK=/fullpath/Android/Sdk/ndk-bundle
~$ cmake
	-D ANDDROID_ABI=armeabi-v7a
    -D ANDROID_FUNCTION_LEVEL_LINKING=ON
    -D ANDROID_NATIVE_API_LEVEL=19
    -D ANDROID_NDK_HOST_X64=ON
    -D ANDROID_NDK_NOEXECSTACK=ON
    -D ANDROID_STL=gnustl_static
    -D BUILD_JPEG=ON
    -D BUILD_PNG=ON
    -D BUILD_PACKAGE=ON
    -D CMAKE_TOOLCHAIN_FILE=/fullpath/opencv-3.4.1/platforms/android/android.toolchain.cmake
    -D ANDROID_SDK=/fullpath/Android/Sdk
    -D ANDROID_FORCE_ARM_BUILD=OFF
    -D ANDROID_NO_UNDEFINED=ON
    -D BUILD_ANDROID=ON
    -D BUILD_ANDROID_EXAMPLES=ON
    -D OPENCV_EXTRA_MODULES_PATH=/fullpath/opencv_contrib-3.4.1/modules
    -D BUILD_PYTHON_SUPPORT=ON
    -D BUILD_opencv_python3=ON
    -D PYTHON_DEFAULT_EXECUTABLE=$HOME/.pyenv/versions/3.6.5/bin/python3.6m
    -D PYTHON_INCLUDE_DIRS=$HOME/.pyenv/versions/3.6.5/include/python3.6m
    -D PYTHON_EXECUTABLE=$HOME/.pyenv/versions/3.6.5/bin/python3.6
    -D PYTHON_LIBRARY=$HOME/.pyenv/versions/3.6.5/lib/libpython3.6m.so.1.0
    -D BUILD_JDK=ON
    -D BUILD_opencv_java=ON
    -D CMAKE_INSTALL_PREFIX=/fullpath/opencv3-android-ndk ../

[...]
--     Linker flags (Release):      -Wl,--fix-cortex-a8 -Wl,--no-undefined -Wl,-allow-shlib-undefined -Wl,--gc-sections -Wl,-z,noexecstack -Wl,-z,relro -Wl,-z,now
--     Linker flags (Debug):        -Wl,--fix-cortex-a8 -Wl,--no-undefined -Wl,-allow-shlib-undefined -Wl,--gc-sections -Wl,-z,noexecstack -Wl,-z,relro -Wl,-z,now
--     ccache:                      NO
--     Precompiled headers:         NO
--     Extra dependencies:          z dl m log
--     3rdparty dependencies:       libcpufeatures libprotobuf libjpeg libwebp libpng libtiff libjasper IlmImf tegra_hal
--
--   OpenCV modules:
--     To be built:                 aruco bgsegm bioinspired calib3d ccalib core datasets dnn dnn_objdetect dpm face features2d flann fuzzy hfs highgui img_hash imgcodecs imgproc java_bindings_generator line_descriptor ml objdetect optflow phase_unwrapping photo plot python_bindings_generator reg rgbd saliency shape stereo stitching structured_light superres surface_matching text tracking ts video videoio videostab xfeatures2d ximgproc xobjdetect xphoto
--     Disabled:                    js world
--     Disabled by dependency:      -
--     Unavailable:                 cnn_3dobj cudaarithm cudabgsegm cudacodec cudafeatures2d cudafilters cudaimgproc cudalegacy cudaobjdetect cudaoptflow cudastereo cudawarping cudev cvv dnn_modern freetype hdf java matlab ovis python2 python3 sfm viz
--     Applications:                tests perf_tests
--     Documentation:               NO
--     Non-free algorithms:         NO
--
--   Android:
--     Android ABI:                 armeabi-v7a
--     STL type:                    gnustl_static
--     Native API level:            android-19
--     SDK target:                  android-19
--     Android NDK:                 /fullpath/Android/Sdk/ndk-bundle-r14b (toolchain: arm-linux-androideabi-4.9)
--     android tool:                /fullpath/3TB-DISK/Android/Sdk/tools/android (Android SDK Tools, revision 25.2.5.)

--
--   GUI:
--
--   Media I/O:
--     ZLib:                        z (ver 1.2.3)
--     JPEG:                        build (ver 90)
--     WEBP:                        build (ver encoder: 0x020e)
--     PNG:                         build (ver 1.6.34)
--     TIFF:                        build (ver 42 - 4.0.9)
--     JPEG 2000:                   build (ver 1.900.1)
--     OpenEXR:                     build (ver 1.7.1)
[...]
--   Java:                          export all functions
--     ant:                         /fullpath/ant/current/bin/ant (ver 1.10.1)
--     Java wrappers:               YES
--     Java tests:                  YES
[...]
--   Install to:                    /fullpath/opencv3-android-ndk

~$ make -j4
[...]

# 编译成功的标志
BUILD SUCCESSFUL
Total time: 6 seconds
[100%] Built target example-color-blob-detection
[100%] Copy project sources: example-tutorial-1-camerapreview
COPYFILES: ... 1 entries (SRC_COPY)
COPYFILES:     ... directory '.../android/tutorial-1-camerapreview' with 5 files
COPYFILES: All files are up-to-date.
[100%] Built target example-tutorial-1-camerapreview_copy_src
Scanning dependencies of target example-tutorial-1-camerapreview
[100%] Updating Android project at /fullpath/opencv-3.4.1/samples/android/tutorial-1-camerapreview. SDK target: android-19
[100%] Generating example-tutorial-1-camerapreview-debug.apk

BUILD SUCCESSFUL
Total time: 6 seconds
[100%] Built target example-tutorial-1-camerapreview
[100%] Copy project sources: example-tutorial-2-mixedprocessing
COPYFILES: ... 1 entries (SRC_COPY)
COPYFILES:     ... directory '.../android/tutorial-2-mixedprocessing' with 5 files
COPYFILES: All files are up-to-date.
[100%] Built target example-tutorial-2-mixedprocessing_copy_src
[100%] Built target mixed_sample
Scanning dependencies of target example-tutorial-2-mixedprocessing
[100%] Updating Android project at /fullpath/opencv-3.4.1/samples/android/tutorial-2-mixedprocessing. SDK target: android-19
[100%] Generating example-tutorial-2-mixedprocessing-debug.apk

BUILD SUCCESSFUL
Total time: 6 seconds
[100%] Built target example-tutorial-2-mixedprocessing
[100%] Copy project sources: example-tutorial-3-cameracontrol
COPYFILES: ... 1 entries (SRC_COPY)
COPYFILES:     ... directory '.../android/tutorial-3-cameracontrol' with 6 files
COPYFILES: All files are up-to-date.
[100%] Built target example-tutorial-3-cameracontrol_copy_src
Scanning dependencies of target example-tutorial-3-cameracontrol
[100%] Updating Android project at /fullpath/opencv-3.4.1/samples/android/tutorial-3-cameracontrol. SDK target: android-19
[100%] Generating example-tutorial-3-cameracontrol-debug.apk

BUILD SUCCESSFUL
Total time: 6 seconds
[100%] Built target example-tutorial-3-cameracontrol


~$ make install

运行完成make install后,所有相关的库文件都会安装到**/fullpath/opencv3-android-ndk**,目录如下:

opencv3-android-ndk$ tree -L 3
.
├── apk
│   └── readme.txt
├── LICENSE
├── README.android
└── sdk
    ├── build.gradle
    ├── etc
    │   ├── haarcascades
    │   ├── lbpcascades
    │   ├── valgrind_3rdparty.supp
    │   └── valgrind.supp
    ├── java
    │   ├── AndroidManifest.xml
    │   ├── gen
    │   ├── lint.xml
    │   ├── project.properties
    │   ├── res
    │   └── src
    └── native
        ├── 3rdparty
        ├── jni
        ├── libs
        └── staticlibs

14 directories, 9 files

Android Studio 集成 OpenCV 测试

这里可以直接导入一个 OpenCV Samples 工程做测试,我编译安装完上述 SDK 后,使用了samples/tutorial-1-camerapreview这个工程做测试,正常情况下,app 会通过 opencv 打开摄像头.

原有工程,添加 OpenCV 支持

创建一个支持 C++的 Android 工程
导入模块, File->New->Import Module ,选择**/fullpath/opencv3-android-ndk** ,这里我把它命名为**:opencv_sdk**, Finish.
如果 IDE 没有报错,
进入 File>Project Structure. 选择app ,点击Dependencides,点击+->3 Module dependency->模块名,
等几分钟,IDE 就会处理完导入库的操作.
如果在File>Project Structure没有看到一个新的模块名opencv_sdk,但是它的目录已经复制到工程目录的根目录下了,就在settings.gradle里的include后面加上如: include ‘:app’,’opencv_sdk’
因为我本次使用的是Android-Studio 3.1的版本,要把build.gradle里的修改成 26以上,不然会出错:

android {
    compileSdkVersion 27
    //buildToolsVersion "27.0.3" // not needed since com.android.tools.build:gradle:3.0.0

    defaultConfig {
        minSdkVersion 14
        targetSdkVersion 26
    }

  [...]
}

导入模块后,IDE 会把 opencv 相关复制工程根目录下,目录名为opencv_sdk.导入后 Android 工程目录如下:

~$ tree -L 1
.
├── app
├── build.gradle
├── gradle
├── gradle.properties
├── gradlew
├── gradlew.bat
├── local.properties
├── opencv3_android.iml
├── opencv_sdk
└── settings.gradle

~$ tree app  -L 4
app
├── app.iml
├── build.gradle
├── CMakeLists.txt
├── libs
├── proguard-rules.pro
└── src
    ├── androidTest
    │   └── java
    │       └── com
    ├── main
    │   ├── AndroidManifest.xml
    │   ├── cpp
    │   │   └── native-lib.cpp
    │   ├── java
    │   │   └── com
    │   └── res
    │       ├── drawable
    │       ├── drawable-v24
    │       ├── layout
    │       ├── menu
    │       ├── mipmap-anydpi-v26
    │       ├── mipmap-hdpi
    │       ├── mipmap-mdpi
    │       ├── mipmap-xhdpi
    │       ├── mipmap-xxhdpi
    │       ├── mipmap-xxxhdpi
    │       ├── raw
    │       └── values
    └── test
        └── java
            └── com

25 directories, 6 files

~$ tree opencv_sdk  -L 3
opencv_sdk
├── build.gradle
├── etc
│   ├── haarcascades
│   │   ├── haarcascade_eye_tree_eyeglasses.xml
│   │   ├── haarcascade_eye.xml
│   │   ├── haarcascade_frontalcatface_extended.xml
│   │   ├── haarcascade_frontalcatface.xml
│   │   ├── haarcascade_frontalface_alt2.xml
│   │   ├── haarcascade_frontalface_alt_tree.xml
│   │   ├── haarcascade_frontalface_alt.xml
│   │   ├── haarcascade_frontalface_default.xml
│   │   ├── haarcascade_fullbody.xml
│   │   ├── haarcascade_lefteye_2splits.xml
│   │   ├── haarcascade_licence_plate_rus_16stages.xml
│   │   ├── haarcascade_lowerbody.xml
│   │   ├── haarcascade_profileface.xml
│   │   ├── haarcascade_righteye_2splits.xml
│   │   ├── haarcascade_russian_plate_number.xml
│   │   ├── haarcascade_smile.xml
│   │   └── haarcascade_upperbody.xml
│   ├── lbpcascades
│   │   ├── lbpcascade_frontalcatface.xml
│   │   ├── lbpcascade_frontalface_improved.xml
│   │   ├── lbpcascade_frontalface.xml
│   │   ├── lbpcascade_profileface.xml
│   │   └── lbpcascade_silverware.xml
│   ├── valgrind_3rdparty.supp
│   └── valgrind.supp
├── java
│   ├── AndroidManifest.xml
│   ├── gen
│   ├── lint.xml
│   ├── project.properties
│   ├── res
│   │   └── values
│   └── src
│       └── org
├── native
│   ├── 3rdparty
│   │   └── libs
│   ├── jni
│   │   ├── abi-armeabi-v7a
│   │   ├── android.toolchain.cmake
│   │   ├── include
│   │   ├── OpenCV-armeabi-v7a.mk
│   │   ├── OpenCVConfig.cmake
│   │   ├── OpenCVConfig-version.cmake
│   │   └── OpenCV.mk
│   ├── libs
│   │   └── armeabi-v7a
│   └── staticlibs
│       └── armeabi-v7a
└── opencv_sdk.iml

19 directories, 34 files

纯 `JNI C++`开发,调用 OPENCV

如果我们要在 Android 工程里的使用 JNI 直接调用 opencv 的 API 函数,如上面工程 src/main/cpp/native-lib.cpp.
需要在app/build.gradle 的 android结点里添加相关路径:


android {

    [...]
    externalNativeBuild {
        cmake {
            path "CMakeLists.txt"
        }
    }

    sourceSets {
        main {
            jni.srcDirs = [jni.srcDirs,'../opencv_sdk/native/jni/include']
            jniLibs.srcDirs = [jniLibs.srcDirs,'../opencv_sdk/native/3rdparty/libs','../opencv_sdk/native/libs']
        }
    }
}

app/CMakeLists.txt里要包含如下信息:


set(pathToOpenCV ${CMAKE_CURRENT_SOURCE_DIR}/../open_sdk )
include_directories(${pathToOpenCV}/native/jni/include) # Not needed for CMake >= 2.8.11

set(CMAKE_VERBOSE_MAKEFILE on)
set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=gnu++11")
add_library( lib_opencv STATIC IMPORTED )
set_target_properties(lib_opencv PROPERTIES IMPORTED_LOCATION
                        ${pathToOpenCV}/native/libs/${ANDROID_ABI}/libopencv_java3.so)
target_link_libraries( # Specifies the target library.
                       native-lib

                       # Links the target library to the log library
                       # included in the NDK.
                       ${log-lib}
                       lib_opencv   # 要加上这lib_opencv 才能链接到opencv的库.
                       )

添加上述路径之后,就可以在src/main/cpp/native-lib.cpp 里添加#include <opencv2/opencv.hpp>.
上述 JNI 方式开发就是写原生的 C++代码调用 API,编译成功后会生成.so的文件,通过 JNI 方式加载这个库文件,或者升级更新这个库文件,不需要修改 Android 的文件.但是不能像 PC 下那样使用,如:imshow(),namedWindow(),createTrackBar(),waitKey(),这些函数是不能用.

谢谢支持

微信二维码:
联系作者

Sunrise 博客

为Android编译OpenCV3_SDK

Python 脚本编译

安装编译工具

CMake 编译方式

编译环境

CMake 单独编译参数

Android Studio 集成 OpenCV 测试

原有工程,添加 OpenCV 支持

纯 `JNI C++`开发,调用 OPENCV

谢谢支持

Python 脚本编译

安装编译工具

CMake 编译方式

编译环境

CMake 单独编译参数

Android Studio 集成 OpenCV 测试

原有工程,添加 OpenCV 支持

纯 JNI C++开发,调用 OPENCV

谢谢支持

纯 `JNI C++`开发,调用 OPENCV