andriod studio 在jni层使用opencv

环境：

AS:4.0

CV:4.5

新建项目

 设置build文件中的版本

sync一下，看看是否编译成功

无报错，运行一遍初始代码，Run一下

运行成功

手机上的软件打开显示的 “hello from C++"

接下来配置Cmake文件

cmake_minimum_required(VERSION 3.4.1)

# ##################### OpenCV 环境 ############################
#设置OpenCV-android-sdk路径
set( OpenCV_DIR F:/opencv/OpenCV-android-sdk/sdk/native/jni )

find_package(OpenCV REQUIRED )
if(OpenCV_FOUND)
    include_directories(${OpenCV_INCLUDE_DIRS})
    message(STATUS "OpenCV library status:")
    message(STATUS "    version: ${OpenCV_VERSION}")
    message(STATUS "    libraries: ${OpenCV_LIBS}")
    message(STATUS "    include path: ${OpenCV_INCLUDE_DIRS}")
else(OpenCV_FOUND)
    message(FATAL_ERROR "OpenCV library not found")
endif(OpenCV_FOUND)

# ###################### 项目原生模块 ###########################

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

target_link_libraries( native-lib
        ${OpenCV_LIBS}
        log
        jnigraphics)

 注意改一下路径

 修改xml文件

修改mainactivity文件

package com.demo.opencv;

import androidx.appcompat.app.AppCompatActivity;

import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.os.Bundle;
import android.view.View;
import android.widget.ImageView;
import android.widget.TextView;

public class MainActivity extends AppCompatActivity implements View.onClickListener {
    private ImageView imageView;

    static {//加载so库
        System.loadLibrary("native-lib");
    }

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        imageView = findViewById(R.id.imageView);
        findViewById(R.id.show).setonClickListener(this);
        findViewById(R.id.process).setonClickListener(this);
    }

    @Override
    public void onClick(View v) {
        if (v.getId() == R.id.show) {
            Bitmap bitmap = BitmapFactory.decodeResource(getResources(), R.drawable.test);
            imageView.setImageBitmap(bitmap);
        } else {
            Bitmap bitmap = BitmapFactory.decodeResource(getResources(), R.drawable.test);
            getEdge(bitmap);
            imageView.setImageBitmap(bitmap);
        }
    }

    //获得Canny边缘
    native void getEdge(Object bitmap);
}

将一张名为test.jpg的图片放置在drawable目录下

 生成头文件

打开Android Studio下方Terminal栏，输入cd appsrcmainjava(所有应用都一样)，回车。然后输入javah -encoding UTF-8 包名.类名(我们这里输入的是javah -encoding UTF-8 com.demo.opencv.NativeActivity，注意，类名后面不要加.java或.class)，回车后，将在appsrcmainjava目录下生成一个头文件，如果提示类文件不存在，则需先build，再执行上述操作。最后将该头文件移动到appsrcmaincpp目录下。

或者，在设置里面新建一个javah

在对mainactivity操作

将生成的.h文件剪切至cpp文件夹目录下

编写native-lib.cpp文件

#include "com_demo_opencv_MainActivity.h"
#include 
#include 

using namespace cv;

extern "C" JNIEXPORT void
JNICALL Java_com_demo_opencv_MainActivity_getEdge
        (JNIEnv *env, jobject obj, jobject bitmap) {
    AndroidBitmapInfo info;
    void *pixels;

    CV_Assert(AndroidBitmap_getInfo(env, bitmap, &info) >= 0);
    CV_Assert(info.format == ANDROID_BITMAP_FORMAT_RGBA_8888 ||
              info.format == ANDROID_BITMAP_FORMAT_RGB_565);
    CV_Assert(AndroidBitmap_lockPixels(env, bitmap, &pixels) >= 0);
    CV_Assert(pixels);
    if (info.format == ANDROID_BITMAP_FORMAT_RGBA_8888) {
        Mat temp(info.height, info.width, CV_8UC4, pixels);
        Mat gray;
        cvtColor(temp, gray, COLOR_RGBA2GRAY);
        Canny(gray, gray, 45, 75);
        cvtColor(gray, temp, COLOR_GRAY2RGBA);
    } else {
        Mat temp(info.height, info.width, CV_8UC2, pixels);
        Mat gray;
        cvtColor(temp, gray, COLOR_RGB2GRAY);
        Canny(gray, gray, 45, 75);
        cvtColor(gray, temp, COLOR_GRAY2RGB);
    }
    AndroidBitmap_unlockPixels(env, bitmap);
}

 运行程序

调试

检验结果