Android Studio NDK 지원 OpenCV 라이브러리 사용 방법

⬛ 패키지 설치

Tools > SDK Manager >NDK, CMake 패키지 선택 후 OK

 

 

⬛ 안드로이드 프로젝트 생성

New Project > Native C++ 선택

 

프로젝트명 기입, Language: Java, Minimum SDK: API 21 (없을 시 Tools에서 설치)

C++ Standard Default, Finish 버튼 클릭

 

⬛ 프로젝트에 OpenCV 라이브러리 추가

OpenCV 깃허브 저장소에서 opencv-4.7.0-android-sdk.zip 설치 후 압축 해제

https://github.com/opencv/opencv/releases

Releases · opencv/opencv

 

1. Android Studio에 라이브러리 모듈 Import

File > New > Import Module 에서 OpenCV-android-sdk 디렉토리 하위에 있는 sdk 디렉토리 선택 후 OK

SDK 모듈이 추가되었다면 다음과 같이 확인할 수 있음.

sdk > build.gradle에서 apply plugin: 'kotlin-android 제거

 

2. App 모듈에서 OpenCV 라이브러리 모듈 사용할 수 있도록 설정

File > Project structure 에서 Dependencies > + 버튼 클릭 > 3. Moduile Dependency

sdk 체크 후 OK > 아래 사진처럼 sdk가 추가됨.

 

⬛ CMake 사용한 NDK와 OpenCV로 카메라 작동 및 라이브러리 사용

카메라를 사용하기 위해서 manifests>AndroidManifest.xml에 permission을 추가해야함.

레이아웃 파일 activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity" >

    <org.opencv.android.JavaCameraView
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:id="@+id/activity_surface_view" />

</LinearLayout>

타이틀 바 제거 themes.xml

<resources xmlns:tools="http://schemas.android.com/tools">
    <!-- Base application theme. -->
    <style name="Theme.Opencvtest2" parent="Theme.MaterialComponents.DayNight.DarkActionBar">
        <!-- Primary brand color. -->
        <item name="colorPrimary">@color/purple_500</item>
        <item name="colorPrimaryVariant">@color/purple_700</item>
        <item name="colorOnPrimary">@color/white</item>
        <!-- Secondary brand color. -->
        <item name="colorSecondary">@color/teal_200</item>
        <item name="colorSecondaryVariant">@color/teal_700</item>
        <item name="colorOnSecondary">@color/black</item>
        <!-- Status bar color. -->
        <item name="android:statusBarColor">?attr/colorPrimaryVariant</item>
        <!-- Customize your theme here. -->
        <!-- No Title Bar-->
        <item name="windowActionBar">false</item>
        <item name="windowNoTitle">true</item>
    </style>
</resources>

java 코드에서 JNI(Java Native Interface) 사용하여 C++ 함수를 호출하여 영상 처리 진행

MainActivity.java

package com.example.opencvtest;

import androidx.appcompat.app.AlertDialog;
import androidx.appcompat.app.AppCompatActivity;

import android.content.DialogInterface;
import android.os.Bundle;
import android.annotation.TargetApi;
import android.content.pm.PackageManager;
import android.os.Build;
import android.util.Log;
import android.view.SurfaceView;
import android.view.WindowManager;
import org.opencv.android.BaseLoaderCallback;
import org.opencv.android.CameraBridgeViewBase;
import org.opencv.android.LoaderCallbackInterface;
import org.opencv.android.OpenCVLoader;
import org.opencv.core.Mat;

import java.util.Collections;
import java.util.List;

import static android.Manifest.permission.CAMERA;


public class MainActivity extends AppCompatActivity
        implements CameraBridgeViewBase.CvCameraViewListener2 {

    private static final String TAG = "opencv";
    private Mat matInput;
    private Mat matResult;

    private CameraBridgeViewBase mOpenCvCameraView;

    public native void ConvertRGBtoGray(long matAddrInput, long matAddrResult);

    static {
        System.loadLibrary("opencv_java4");
        System.loadLibrary("native-lib");
    }



    private BaseLoaderCallback mLoaderCallback = new BaseLoaderCallback(this) {
        @Override
        public void onManagerConnected(int status) {
            switch (status) {
                case LoaderCallbackInterface.SUCCESS:
                {
                    mOpenCvCameraView.enableView();
                } break;
                default:
                {
                    super.onManagerConnected(status);
                } break;
            }
        }
    };


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN,
                WindowManager.LayoutParams.FLAG_FULLSCREEN);
        getWindow().setFlags(WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON,
                WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON);

        setContentView(R.layout.activity_main);

        mOpenCvCameraView = (CameraBridgeViewBase)findViewById(R.id.activity_surface_view);
        mOpenCvCameraView.setVisibility(SurfaceView.VISIBLE);
        mOpenCvCameraView.setCvCameraViewListener(this);
        mOpenCvCameraView.setCameraIndex(0); // front-camera(1),  back-camera(0)
    }

    @Override
    public void onPause()
    {
        super.onPause();
        if (mOpenCvCameraView != null)
            mOpenCvCameraView.disableView();
    }

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

        if (!OpenCVLoader.initDebug()) {
            Log.d(TAG, "onResume :: Internal OpenCV library not found.");
            OpenCVLoader.initAsync(OpenCVLoader.OPENCV_VERSION_3_2_0, this, mLoaderCallback);
        } else {
            Log.d(TAG, "onResum :: OpenCV library found inside package. Using it!");
            mLoaderCallback.onManagerConnected(LoaderCallbackInterface.SUCCESS);
        }
    }


    public void onDestroy() {
        super.onDestroy();

        if (mOpenCvCameraView != null)
            mOpenCvCameraView.disableView();
    }

    @Override
    public void onCameraViewStarted(int width, int height) {

    }

    @Override
    public void onCameraViewStopped() {

    }

    @Override
    public Mat onCameraFrame(CameraBridgeViewBase.CvCameraViewFrame inputFrame) {

        matInput = inputFrame.rgba();

        if ( matResult == null )

            matResult = new Mat(matInput.rows(), matInput.cols(), matInput.type());

        ConvertRGBtoGray(matInput.getNativeObjAddr(), matResult.getNativeObjAddr());

        return matResult;
    }


    protected List<? extends CameraBridgeViewBase> getCameraViewList() {
        return Collections.singletonList(mOpenCvCameraView);
    }

    private static final int CAMERA_PERMISSION_REQUEST_CODE = 200;


    protected void onCameraPermissionGranted() {
        List<? extends CameraBridgeViewBase> cameraViews = getCameraViewList();
        if (cameraViews == null) {
            return;
        }
        for (CameraBridgeViewBase cameraBridgeViewBase: cameraViews) {
            if (cameraBridgeViewBase != null) {
                cameraBridgeViewBase.setCameraPermissionGranted();
            }
        }
    }

    @Override
    protected void onStart() {
        super.onStart();
        boolean havePermission = true;
        if (Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
            if (checkSelfPermission(CAMERA) != PackageManager.PERMISSION_GRANTED) {
                requestPermissions(new String[]{CAMERA}, CAMERA_PERMISSION_REQUEST_CODE);
                havePermission = false;
            }
        }
        if (havePermission) {
            onCameraPermissionGranted();
        }
    }

    @Override
    @TargetApi(Build.VERSION_CODES.M)
    public void onRequestPermissionsResult(int requestCode, String[] permissions, int[] grantResults) {
        if (requestCode == CAMERA_PERMISSION_REQUEST_CODE && grantResults.length > 0
                && grantResults[0] == PackageManager.PERMISSION_GRANTED) {
            onCameraPermissionGranted();
        }else{
            showDialogForPermission("앱을 실행하려면 퍼미션을 허가하셔야합니다.");
        }
        super.onRequestPermissionsResult(requestCode, permissions, grantResults);
    }


    @TargetApi(Build.VERSION_CODES.M)
    private void showDialogForPermission(String msg) {

        AlertDialog.Builder builder = new AlertDialog.Builder( MainActivity.this);
        builder.setTitle("알림");
        builder.setMessage(msg);
        builder.setCancelable(false);
        builder.setPositiveButton("예", new DialogInterface.OnClickListener() {
            public void onClick(DialogInterface dialog, int id){
                requestPermissions(new String[]{CAMERA}, CAMERA_PERMISSION_REQUEST_CODE);
            }
        });
        builder.setNegativeButton("아니오", new DialogInterface.OnClickListener() {
            public void onClick(DialogInterface arg0, int arg1) {
                finish();
            }
        });
        builder.create().show();
    }


}

 

MainActivity.java 파일에 ConvertRGBtoGray 함수가 빨간색으로 보이는데, 마우스 커서를 가져가면 보이는 빨간 전구를 클릭하고 메뉴에서 “Create JNI function for ConvertRGBtoGray” > “native-lib.cpp” 선택

native-lib.cpp

#include <jni.h>
#include <string>
#include <opencv2/opencv.hpp>

using namespace cv;

extern "C"
JNIEXPORT void JNICALL
Java_com_tistory_webnautes_useopencvwithcmake_MainActivity_ConvertRGBtoGray(JNIEnv *env,
                                jobject thiz,
                                jlong mat_addr_input,
                                jlong mat_addr_result) {
    // TODO: implement ConvertRGBtoGray()
    Mat &matInput = *(Mat *)mat_addr_input;
    Mat &matResult = *(Mat *)mat_addr_result;

    cvtColor(matInput, matResult, COLOR_RGBA2GRAY);
}

CMakeLists.txt를 다음 코드로 대체 (pathPROJECT 경로를 실제 프로젝트 경로로 변경해야함)

# 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)

set(pathPROJECT C:/Users/user/AndroidStudioProjects/opencvtest) # 수정필요
set(pathOPENCV ${pathPROJECT}/sdk)
set(pathLIBOPENCV_JAVA ${pathOPENCV}/native/libs/${ANDROID_ABI}/libopencv_java4.so)

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

include_directories(${pathOPENCV}/native/jni/include)


# Creates and names a library, sets it as either STATIC
# or SHARED, and provides the relative paths to its source code.
# You can define multiple libraries, and CMake builds them for you.
# Gradle automatically packages shared libraries with your APK.

add_library( # Sets the name of the library.
        native-lib

        # Sets the library as a shared library.
        SHARED

        # Provides a relative path to your source file(s).
        ${pathPROJECT}/app/src/main/cpp/native-lib.cpp )



add_library( lib_opencv SHARED IMPORTED )

set_target_properties(lib_opencv PROPERTIES IMPORTED_LOCATION ${pathLIBOPENCV_JAVA})


# Searches for a specified prebuilt library and stores the path as a
# variable. Because CMake includes system libraries in the search path by
# default, you only need to specify the name of the public NDK library
# you want to add. CMake verifies that the library exists before
# completing its build.

find_library( # Sets the name of the path variable.
        log-lib

        # Specifies the name of the NDK library that
        # you want CMake to locate.
        log )

# Specifies libraries CMake should link to your target library. You
# can link multiple libraries, such as libraries you define in this
# build script, prebuilt third-party libraries, or system libraries.

target_link_libraries( # Specifies the target library.
        native-lib

        lib_opencv

        # Links the target library to the log library
        # included in the NDK.
        ${log-lib} )

Sync Now 클릭 혹은 메뉴 > File > Sync Project with Gradle Files > Gradle build