Use of OpenCV in the Android environment -- environment construction (1)

OpenCv environment construction

1. OpenCV SDK download

openCv official website download
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2. Create a C++ project in Android Studio

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3. The so library of openCV is loaded into the project

Create a new jniLibs under the src->main directory
Download the so library of the platform corresponding to the opencv-4.1.0-android-sdk\OpenCV-android-sdk\sdk\native\libs directory of the openCv sdk

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4. Load the header file

Load the header file of the header file directory include under the sdk directory into the project
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5. Configure the CmakeLists file



cmake_minimum_required(VERSION 3.10.2)


project("open")


include_directories(include)

add_library(
        open


        SHARED


        native-lib.cpp)



find_library(
        log-lib

        log)


set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -L${CMAKE_SOURCE_DIR}/../jniLibs/${CMAKE_ANDROID_ARCH_ABI}")

target_link_libraries(
        open
        opencv_java4
        ${
    
    log-lib})

6. Gradle file configuration

 defaultConfig {
    
    
     
        externalNativeBuild {
    
    
            cmake {
    
    
                cppFlags ''
                abiFilters 'armeabi-v7a'
            }
        }

        ndk{
    
    
            abiFilters 'armeabi-v7a'
        }

    }

7. Verify openCV in jni

#include <jni.h>
#include <string>


#include "opencv2/opencv.hpp"

using namespace cv;

extern "C" JNIEXPORT jstring JNICALL
Java_com_xyx_open_MainActivity_stringFromJNI(
        JNIEnv* env,
        jobject /* this */) {
    
    
    std::string hello = "Hello from C++";

    Mat src=imread("sdcard/test_20220811161338.png");

    cvtColor(src,src,COLOR_BGR2GRAY);

    imwrite("/sdcard/test1.png",src);

    src.release();

    return env->NewStringUTF(hello.c_str());
}

8. Project compilation

Simple test, a photo in the sdcard directory is processed by opencv, the output is successful, and the use environment of openCV on Android is no problem.