AndroidStudio使用CMake编译方式的NDK opencv开发

其实网上关于 AndroidStudio使用CMake编译方式的NDK opencv开发  类似的博客已经有很多了，但是为什么我还要去写这篇博客呢，因为我在引用OpenCV库时踩了很多坑，所以特别记录一下。

 

搭建步骤：

 

一.创建AS支持C++的工程

 

File------>New-------------->New Project

 

项目结构

 

 

创建jniLibs

src------>main------>jinLibs

复制OpenCV-android-sdk\sdk\native\libs放在jinLibs目录下    opencv-3.4.1-android-sdk下载地址

 

 

解压后文件目录：

 

 

CMakeLists.txt配置

 

# For more information about using CMake with Android Studio, read the
# documentation: https://d.android.com/studio/projects/add-native-code.html

# Sets the minimum version of CMake required to build the native library.

cmake_minimum_required(VERSION 3.4.1)


#工程路径
set(pathToProject E:/openCV/TestCpp)

  # 支持 -std=gnu++11

  set(CMAKE_VERBOSE_MAKEFILE on)
  set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=gnu++11")


  # CMAKE_SOURCE_DIR 是 CMakeLists.txt 所在的目录

#CPP文件夹下带编译的cpp文件
add_library( native-lib SHARED src/main/cpp/native-lib.cpp)

#OpenCV-android-sdk路径
  set(pathToOpenCV E:/openCV/opencv-3.4.2-android-sdk/OpenCV-android-sdk)

  #配置加载native依赖
  include_directories( ${pathToOpenCV}/sdk/native/jni/include )

#动态方式加载opencv的动态库
add_library(libopencv SHARED IMPORTED)
#引入libopencv_java3.so文件
set_target_properties(libopencv PROPERTIES IMPORTED_LOCATION
            ${CMAKE_SOURCE_DIR}/src/main/jniLibs/libs/${ANDROID_ABI}/libopencv_java3.so)

#C++日志
find_library(log-lib log )

  target_link_libraries(  native-lib ${log-lib} libopencv )

 

build.gradle配置

 

apply plugin: 'com.android.application'

android {
    compileSdkVersion 28
    defaultConfig {
        applicationId "com.example.administrator.testcpp"
        minSdkVersion 15
        targetSdkVersion 28
        versionCode 1
        versionName "1.0"
        testInstrumentationRunner "android.support.test.runner.AndroidJUnitRunner"
        externalNativeBuild {
            cmake {
                cppFlags "-std=c++11 -frtti -fexceptions"
                abiFilters 'x86', 'x86_64', 'armeabi-v7a', 'arm64-v8a'
            }
        }


        ndk{
            abiFilters 'x86', 'x86_64', 'armeabi-v7a', 'arm64-v8a'
        }
    }


    sourceSets {
        main {
            jniLibs.srcDirs = ['src/main/jniLibs/libs']
        }
    }
    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
        }
    }

    externalNativeBuild {
        cmake {
            path "CMakeLists.txt"
        }

    }

}

dependencies {
    implementation fileTree(dir: 'libs', include: ['*.jar'])
    implementation 'com.android.support:appcompat-v7:28.0.0-rc01'
    implementation 'com.android.support.constraint:constraint-layout:1.1.2'
    testImplementation 'junit:junit:4.12'
    androidTestImplementation 'com.android.support.test:runner:1.0.2'
    androidTestImplementation 'com.android.support.test.espresso:espresso-core:3.0.2'
}

 

MainActivity应用

 

public class MainActivity extends AppCompatActivity {

    // Used to load the 'native-lib' library on application startup.
    static {
        System.loadLibrary("native-lib");
        System.loadLibrary("opencv_java3");
    }

    private ImageView imageView;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        // Example of a call to a native method
        TextView tv = (TextView) findViewById(R.id.sample_text);
        imageView = this.findViewById(R.id.imageView);
        tv.setText(stringFromJNI());

        this.findViewById(R.id.button2).setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                grayPic();
            }
        });
    }


    private void grayPic(){
        Bitmap bmp = BitmapFactory.decodeResource(getResources(),R.drawable.card);
        int w = bmp.getWidth();
        int h = bmp.getHeight();
        int[] pixels = new int[w*h];
        bmp.getPixels(pixels, 0, w, 0, 0, w, h);
        //recall JNI
        int[] resultInt =getGrayImag(pixels, w, h);
        Bitmap resultImg = Bitmap.createBitmap(w, h, Bitmap.Config.ARGB_8888);
        resultImg.setPixels(resultInt, 0, w, 0, 0, w, h);
        imageView.setImageBitmap(resultImg);
    }

    /**
     * A native method that is implemented by the 'native-lib' native library,
     * which is packaged with this application.
     */
    public native String stringFromJNI();


    /**
     * 获取处理的图片
     * @return
     * @param pixels
     * @param w
     * @param h
     */
    public native int [] getGrayImag(int[] pixels, int w, int h);


    @Override
    protected void onResume() {
        super.onResume();

    }
}

 

native-lib.cpp

 

#include 
#include 
#include 
#include 

extern "C" JNIEXPORT jstring

JNICALL
Java_com_example_administrator_testcpp_MainActivity_stringFromJNI(
        JNIEnv *env,
        jobject /* this */) {
    std::string hello = "Hello from C++";
    return env->NewStringUTF(hello.c_str());
}
extern "C"
JNIEXPORT jintArray JNICALL
Java_com_example_administrator_testcpp_MainActivity_getGrayImag(JNIEnv *env, jobject instance,
                                                                jintArray pixels_, jint w, jint h) {
    jint *pixels = env->GetIntArrayElements(pixels_, NULL);

    // TODO
    if (pixels == NULL) {
        return NULL;
    }
    cv::Mat imgData(h, w, CV_8UC4, pixels);
    uchar *ptr = imgData.ptr(0);
    for (int i = 0; i < w * h; i++) {
        int grayScale = (int) (ptr[4 * i + 2] * 0.299 + ptr[4 * i + 1] * 0.587
                               + ptr[4 * i + 0] * 0.114);
        ptr[4 * i + 1] = (uchar) grayScale;
        ptr[4 * i + 2] = (uchar) grayScale;
        ptr[4 * i + 0] = (uchar) grayScale;
    }

    int size = w * h;
    jintArray result = env->NewIntArray(size);
    env->SetIntArrayRegion(result, 0, size, pixels);
    env->ReleaseIntArrayElements(pixels_, pixels, 0);
    return result;
}

 

执行前效果图

 

 

执行后

 

到此结束！！！