android studio JNI教程opencv 基于Android studio3.6的JNI教程之opencv实例详解
watersink 人气:0基本环境:
(1)新建工程OpenCVDemo,选择,一定要选择Native c++类型,最后要选c++14支持。
(2)File->Project Structure->SDK Location,设置这3个路径,NDK选择r14b。
(3)任意找一张图片,复制到res/drawable。
(4)修改布局文件res/layout/ activity_main.xml
<?xml version="1.0" encoding="utf-8"?> <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="match_parent" android:layout_height="match_parent"> <ImageView android:id="@+id/imageView" android:layout_width="match_parent" android:layout_height="match_parent" /> <LinearLayout android:layout_width="match_parent" android:layout_height="wrap_content" android:layout_alignParentBottom="true" android:orientation="horizontal"> <Button android:id="@+id/show" android:layout_width="match_parent" android:layout_height="wrap_content" android:layout_weight="1" android:text="show" /> <Button android:id="@+id/process" android:layout_width="match_parent" android:layout_height="wrap_content" android:layout_weight="1" android:text="process" /> </LinearLayout> </RelativeLayout>
(5)修改java文件,app/src/main/java/ com.example.opencvdemo/ MainActivity
主要修改包括修改
继承OnClickListener类,
修改onCreate方法
增加c++的接口函数,getEdge
实现点击按钮的方法,
整体代码如下,
(6)Termi
package com.example.opencvdemo; 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{ // Used to load the 'native-lib' library on application startup. static { 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); } /** * A native method that is implemented by the 'native-lib' native library, * which is packaged with this application. */ //获得Canny边缘 public native void getEdge(Object bitmap); private ImageView imageView; @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); } } }
nal下进入app\src\main\java这一层目录,执行,
javah com.example.opencvdemo.MainActivity
将生成的com_example_opencvdemo_MainActivity.h,剪切到app/src/main/cpp目录下。
(7)修改app/src/main/cpp下面的native-lib.cpp,主要通过c++实现getEdge方法,主要代码如下,
#include <jni.h> #include <string> #include "com_example_opencvdemo_MainActivity.h" #include <android/bitmap.h> #include <opencv2/opencv.hpp> using namespace cv; extern "C" JNIEXPORT void JNICALL Java_com_example_opencvdemo_MainActivity_getEdge(JNIEnv *env, jobject obj, jobject bitmap){ // TODO: implement getEdge() 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, 125, 225); 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, 125, 225); cvtColor(gray, temp, COLOR_GRAY2RGB); } AndroidBitmap_unlockPixels(env, bitmap); }
(8)修改CMakeLists.txt
包括增加opencv包含路径,增加opencv链接,增加目标库的链接(OpenCV_LIBS和jnigraphics)
全部代码如下,
# 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) # 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. #设置OpenCV-android-sdk路径 set( OpenCV_DIR E:/Android/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: ${OpenCV_INCLUDE_DIRS}") else(OpenCV_FOUND) message(FATAL_ERROR "OpenCV library not found") endif(OpenCV_FOUND) set(CMAKE_SHARED_LINKER_FLAGS "${CMAKE_SHARED_LINKER_FLAGS} -Wl,--exclude-libs,libippicv.a -Wl,--exclude-libs,libippiw.a") 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). native-lib.cpp ) # 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 ${OpenCV_LIBS} jnigraphics # Links the target library to the log library # included in the NDK. ${log-lib} )
(9)修改app/build.gradle
主要增加cmake的cppFlags,arguments
全部代码如下,
apply plugin: 'com.android.application' android { compileSdkVersion 29 buildToolsVersion "29.0.3" defaultConfig { applicationId "com.example.opencvdemo" minSdkVersion 16 targetSdkVersion 29 versionCode 1 versionName "1.0" testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner" externalNativeBuild { cmake { cppFlags "-std=c++14 -frtti -fexceptions" arguments '-DANDROID_STL=gnustl_shared' //支持C++异常处理标准模板快,ndk16+需要注释 //abiFilters "armeabi-v7a", "arm64-v8a", "x86_64" } } } buildTypes { release { minifyEnabled false proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro' } } externalNativeBuild { cmake { path "src/main/cpp/CMakeLists.txt" version "3.10.2" } } } dependencies { implementation fileTree(dir: 'libs', include: ['*.jar']) implementation 'androidx.appcompat:appcompat:1.1.0' implementation 'androidx.constraintlayout:constraintlayout:1.1.3' testImplementation 'junit:junit:4.12' androidTestImplementation 'androidx.test.ext:junit:1.1.1' androidTestImplementation 'androidx.test.espresso:espresso-core:3.2.0' }
(10)整体目录结构如下,
运行程序,
代码链接:
References:
https://www.jianshu.com/p/6e16c0429044
https://www.bilibili.com/video/av55834524/
总结
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