Android NDK开发中引入OpenCV库

2019-02-27

Android NDK开发中，我们作图片处理时，运用到OpenCV第三方库，这时需要倒入OpenCV SDK到Ａndroid Studio项目中.

想了解更多代码，可以查看我的github代码

如下是导入OpenCV到Android Studio项目的步骤。（如果麻烦，直接把我项目的module导入你的项目中，修改CMake文件和gradle）

在OpenCV官方上下载opencv android sdk包。https://opencv.org/releases.html
在Android Studio创建新的module
Library name: OpenCV
Module name: opencv
Package name: org.opencv
复制opencv_sdk_path/sdk/java/src下的所有文件到your_project_path/opencv/src/main/java目录下
在main的目录下创建一个路径目录aidl/org/opencv/engine，以及把java/org/opencv/engine/OpencOpenCVEngineInterface.aidl文件移动到刚创建的目录下
复制资源文件，复制opencv_sdk_path/sdk/java/res下所有文件到your_project_path/opencv/src/main/res目录下
在your_project_opencv/src目录下创建sdk目录，并把opencv_sdk_path/sdk/native所有文件复制到刚创建的目录下

在opencv module下创建CMakeLists.txt文件，并添加如下代码

    cmake_minimum_required(VERSION 3.4.1)

    set(OpenCV_DIR "src/sdk/native/jni")
    find_package(OpenCV REQUIRED)
    message(STATUS "OpenCV libraries: ${OpenCV_LIBS}")
    include_directories(${OpenCV_INCLUDE_DIRS})
    ```  
8. 修改```opencv module```的```build.gradle```文件，如下
    ```gradle
    android {
        compileSdkVersion 28
        
        defaultConfig {
            minSdkVersion 19
            targetSdkVersion 28
            versionCode 1
            versionName "1.0"

            testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"

            externalNativeBuild {
                cmake {
                    cppFlags "-frtti -fexceptions"
                    // 根据你电脑配置添加或删除这些类型
                    abiFilters 'x86', 'x86_64', 'armeabi-v7a', 'arm64-v8a'
                }
            }
        }

        buildTypes {
            release {
                minifyEnabled false
                proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
            }
        }

        externalNativeBuild {
            cmake {
                path "CMakeLists.txt"
            }
        }
        sourceSets {
            main {
                jni.srcDirs = [jni.srcDirs, 'src/sdk/native/jni/include']
                jniLibs.srcDirs = [jniLibs.srcDirs, 'src/sdk/native/3rdparty/libs', 'src/sdk/native/libs']
            }
        }

    }

在app module同样创建CMakeLists.txt文件，添加如下代码

cmake_minimum_required(VERSION 3.4.1)

add_library(native-lib
        SHARED
        native-lib.cpp)

# Include libraries needed for hello-jni lib
target_link_libraries(native-lib
        android
        log)

set(OpenCV_DIR "../../../../opencv/src/sdk/native/jni") #根据CMakeLists.txt路径修改(相对目录)
find_package(OpenCV REQUIRED)
message(STATUS "OpenCV libraries: ${OpenCV_LIBS}")
target_link_libraries(native-lib
        ${OpenCV_LIBS})

修改app module的build.gradle文件，如下

android {
    compileSdkVersion 28
    defaultConfig {
        applicationId "com.coldwizards.nativedemo"
        minSdkVersion 21
        targetSdkVersion 28
        versionCode 1
        versionName "1.0"
        testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
        externalNativeBuild {
            cmake {
                cppFlags "-frtti -fexceptions"
                // 根据你电脑配置添加或删除这些类型
                abiFilters 'x86', 'x86_64', 'armeabi-v7a', 'arm64-v8a'
            }
        }
    }

    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
        }
    }

    externalNativeBuild {
        cmake {
            version '3.10.2'
            path "src/main/cpp/CMakeLists.txt"
        }
    }
}

同步gradle。在C++文件中是否可以include<opencv2/opencv.hpp>
如果打包完成，在分析apk中可以查看到opencv的so文件

步骤完成。

如有遇到什么问题可以在github上提问。