基于Android studio3.6的JNI教程之opencv实例详解 - 移动开发

博主:xiaoweixiaowei 2023-01-18 条评论

基本环境:

Android studio3.6

NDK:r14b(尽量使用该版本)

Opencv3.4.1 android sdk

(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,

基于Android studio3.6的JNI教程之opencv实例详解 - 移动开发
#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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发布于:2023-01-18,除非注明,否则均为 主机评测原创文章,转载请注明出处。