Android Studio下OpenCV及JNI开发

AS下配置OpenCV环境

1.下载OpenCV4Android安装包，本实例中使用OpenCV3.1。解压后问价目录如下：

• apk：OpenCV_3.1.0_Manager_3.10安装包，Android OpenCV手机端使用
• samples：样例代码
• sdk：Android开发程序使用SDK

2.新建project，点击file->new modular，选择OpenCV-android-sdk\sdk\java目录，确认。

3.点击file->Project Structure，选择app，添加dependencies->modular dependency，选择OpenCV3.1，确认

4.最后修改openCVLibrary310下build.gradle中配置，使其与app目录下build.gradle相同。

//openCVLibrary310下build.gradle
android {
    compileSdkVersion 23
    buildToolsVersion "23.0.2"

    defaultConfig {
        minSdkVersion 15
        targetSdkVersion 23
    }

至此AS下OpenCV配置已经结束，使用样例中的代码进行测试，此不赘述。

OpenCV JNI配置

1.本示例中对图像进行轮廓提取，程序主体使用c++实现。
在MainActivity中添加如下函数public static native int[] ImgFun(int []buf,int w,int h);

2.使用javah生成其所对应的头文件：

3.在main目录下新建jni文件夹，将生成的头文件放入该文件夹下，向其中添加ImgFun.cpp Android.mk Application.mk文件。分别写入如下代码：

#Android.mk中添加代码：
LOCAL_PATH :=$(call my-dir)
include $(CLEAR_VARS)
OPENCV_LIB_TYPE:=STATIC
ifeq ("$(wildcard $(OPENCV_MK_PATH))","")
# include指向自己OpenCV-android-sdk\sdk\native\jni\OpenCV.mk对应位置
include D:\download\OpenCV-3.1.0-android-sdk\OpenCV-android-sdk\sdk\native\jni\OpenCV.mk
else
include $(OPENCV_MK_PATH)
endif

LOCAL_MODULE :=ImgFun
LOCAL_SRC_FILES :=ImgFun.cpp
LOCAL_LDLIBS += -lm -llog
include $(BUILD_SHARED_LIBRARY)

# Application.mk写入代码如下：
APP_STL := gnustl_static
APP_CPPFLAGS := -frtti -fexceptionsAPP_ABI := armeabi-v7a

4.向app目录下build.gradle android{}中加入如下代码：

sourceSets.main{
        jniLibs.srcDir 'src/main/libs' //set .so files directory to libs
        jni.srcDirs = [] //disable automatic ndk-build call
    }
// call regular ndk-build(.cmd) script from app directory
    task ndkBuild(type:Exec) { commandLine 'D:\\Users\\XXX\\AppData\\Local\\Android\\sdk\\ndk-bundle\\ndk-build.cmd', '-C', file('src/main').absolutePath//windows系统下的操作；将路径替换为自己NDK所在位置；tasks.withType(JavaCompile) {compileTask -> compileTask.dependsOnndkBuild }

记得在gradle.property中加上：android.useDeprecatedNdk=true;
并且将NDK目录加入到local.properties中：

ndk.dir=D\:\\Users\\kangdekai\\AppData\\Local\\Android\\sdk\\ndk-bundle
sdk.dir=D\:\\Users\\kangdekai\\AppData\\Local\\Android\\sdk

此时build project便可以看到生成的ImgFun.so文件（第一次竟然因为项目名称有特殊符号没有成功）

5.定义ImgFun.cpp如下：

#include "com_example_jniopencv_MainActivity.h"
#include <stdio.h>
#include <stdlib.h>
#include <opencv2/opencv.hpp>
using namespace cv;
IplImage * change4channelTo3InIplImage(IplImage * src);

extern "C" {
JNIEXPORT jintArray JNICALL Java_com_example_jniopencv_MainActivity_ImgFun
        (JNIEnv *, jclass, jintArray, jint, jint);
JNIEXPORT jintArray JNICALL Java_com_example_jniopencv_MainActivity_ImgFun
        (JNIEnv *env, jclass obj, jintArray buf, jint w, jint h) {

    jint *cbuf;
    cbuf = env->GetIntArrayElements(buf, false);
    if (cbuf == NULL) {
        return 0;
    }

    Mat myimg(h, w, CV_8UC4, (unsigned char*) cbuf);
    IplImage image=IplImage(myimg);
    IplImage* image3channel = change4channelTo3InIplImage(&image);

IplImage* pCannyImage=cvCreateImage(cvGetSize(image3channel),IPL_DEPTH_8U,1);

    cvCanny(image3channel,pCannyImage,50,150,3);

    int* outImage=newint[w*h];
    for(int i=0;i<w*h;i++)
    {
        outImage[i]=(int)pCannyImage->imageData[i];
    }

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

IplImage * change4channelTo3InIplImage(IplImage * src) {
    if (src->nChannels != 4) {
        return NULL;
    }

    IplImage * destImg = cvCreateImage(cvGetSize(src), IPL_DEPTH_8U, 3);
    for (int row =0; row < src->height; row++) {
        for (int col =0; col < src->width; col++) {
            CvScalar s = cvGet2D(src, row, col);
            cvSet2D(destImg, row, col, s);
        }
    }

    return destImg;
}

定义MainActivity如下：

static {
        System.loadLibrary("ImgFun");
    }
    public static native int[] ImgFun(int []buf,int w,int h);

    ImageView mIv;
    Button btnNdk,btnRtn;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        TextView mtv=(TextView)findViewById(R.id.tv1);
//        Test mytest=new Test();
//        mtv.setText(mytest.myFun());
        mtv.setText("你好！");

        btnNdk=(Button)findViewById(R.id.button1);
        btnRtn=(Button)findViewById(R.id.button2);
        btnRtn.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {

mIv=(ImageView)findViewById(R.id.iV);
                Bitmap img = ((BitmapDrawable) getResources().getDrawable(R.drawable.image)).getBitmap();
                mIv.setImageBitmap(img);
            }
        });
        btnNdk.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                long current = System.currentTimeMillis();
                Bitmap img1 = ((BitmapDrawable) getResources().getDrawable(
                        R.drawable.image)).getBitmap();
                int w = img1.getWidth(), h = img1.getHeight();
                int[] pix = new int[w * h];
                img1.getPixels(pix, 0, w, 0, 0, w, h);
                int[] resultInt = ImgFun(pix, w, h);
                Bitmap resultImg = Bitmap.createBitmap(w, h, Bitmap.Config.RGB_565);
                resultImg.setPixels(resultInt,0, w, 0, 0, w, h);
                long performance = System.currentTimeMillis() - current;
                mIv.setImageBitmap(resultImg);
            }

     });
    }

6.运行程序，便可看到如下效果了~

参考博文：
1.android studio 使用 jni 编译 opencv 完整实例 之 图像边缘检测！从此在andrid中自由使用 图像匹配、识别、检测
2.Android Studio 配置OpenCV、NDK，并用Jni调用OpenCV
3.在Android中使用JNI调用Opencv本地代码 配置方式 边缘检测 范例代码
4.OpenCV在Android环境下的使用方法
5.OpenCV4Android Samples