• Android基于opencv4.6.0实现人脸识别功能

    前言

    步骤：

    1.整合opencv

    2.获取相机的SurfaceView传到native层去检测(亦或是不断的获取SurfaceView的Bitmap，传到native层)

    3.检测人脸，在本地保存人脸特征信息

    4.上传至后台(不实现)

    人脸识别实现的思路(例：人脸登录)

    1.人脸信息录入

    1.1获取相机的Bitmap，检测人脸(保证人脸信息比较精准) 人脸要足够大，当前范围内人脸只能有一张人脸，正常、眨眼睛、张嘴巴(3张人脸信息)

    1.2获取到人脸必须要保存人脸特征信息，然后上传至后台(后台会再次做算法优化)，保存到数据库

    2.人脸特征值匹配

    2.1获取相机的Bitmap，检测人脸(保证人脸信息比较精准) 人脸要足够大，当前范围内人脸只能有一张人脸，正常、眨眼睛、张嘴巴(3张人脸信息)

    2.2从后台去查询用户进行登录

    一.Android Studio配置opencv

    1.opencv资源获取

    opencv官网：Home - OpenCV 

    opencv最新的版本是4.6.0于2022年06月07日发布，4.6.0网址：OpenCV 4.6.0 Is Now Available! - OpenCV

    opencv 4.6.0android sdk 下载链接https://nchc.dl.sourceforge.net/project/opencvlibrary/4.6.0/opencv-4.6.0-android-sdk.zip

    2.解压opencv-4.6.0-android-sdk.zip文件

    解压之后的文件夹:OpenCV-android-sdk

    ​

    ​

    samples： 所有与android相关的一些示例代码，基本全部是java代码，封装了很多功能(图片转成灰度，高斯模糊，边缘检测)

    sdk：所有的资源，so库，头文件，NDK自己动手写

    源码下载链接：https://github.com/opencv/opencv/archive/4.6.0.zip

    3.新建Android项目(native c++)

    C++ Standard 选择C++11

     

     在main目录下新建jni文件夹

     将OpenCV-android-sdk\sdk\native\jni下的include文件夹复制至项目中的jni文件夹下

     

     将OpenCV-android-sdk\sdk\native\libs下的armeabi-v7a文件夹复制至jni文件夹下

     

     3.1配置CMakeLists.txt

    引入头文件

     添加opencv库并设置目标属性(注意路径)

     添加目标链接库opencv-lib

     CMakeLists.txt内容：

    1. # For more information about using CMake with Android Studio, read the
    2. # documentation: https://d.android.com/studio/projects/add-native-code.html
    3.  
    4. # Sets the minimum version of CMake required to build the native library.
    5.  
    6. cmake_minimum_required(VERSION 3.10.2)
    7.  
    8. # Declares and names the project.
    9.  
    10. project("opencvtestapplication")
    11. #需要引入我们头文件，以这个配置的目录为基准
    12. include_directories(${CMAKE_SOURCE_DIR}/../jni/include)
    13.  
    14. # Creates and names a library, sets it as either STATIC
    15. # or SHARED, and provides the relative paths to its source code.
    16. # You can define multiple libraries, and CMake builds them for you.
    17. # Gradle automatically packages shared libraries with your APK.
    18.  
    19. add_library( # Sets the name of the library.
    20.              native-lib
    21.  
    22.              # Sets the library as a shared library.
    23.              SHARED
    24.  
    25.              # Provides a relative path to your source file(s).
    26.              native-lib.cpp )
    27. # 添加opencv的库
    28. add_library(
    29.         opencv-lib
    30.         SHARED
    31.         IMPORTED)
    32. set_target_properties(
    33.         opencv-lib
    34.         PROPERTIES IMPORTED_LOCATION
    35.         ${CMAKE_SOURCE_DIR}/../jni/armeabi-v7a/libopencv_java4.so)
    36.  
    37. # Searches for a specified prebuilt library and stores the path as a
    38. # variable. Because CMake includes system libraries in the search path by
    39. # default, you only need to specify the name of the public NDK library
    40. # you want to add. CMake verifies that the library exists before
    41. # completing its build.
    42.  
    43. find_library( # Sets the name of the path variable.
    44.               log-lib
    45.  
    46.               # Specifies the name of the NDK library that
    47.               # you want CMake to locate.
    48.               log )
    49.  
    50. # Specifies libraries CMake should link to your target library. You
    51. # can link multiple libraries, such as libraries you define in this
    52. # build script, prebuilt third-party libraries, or system libraries.
    53.  
    54. target_link_libraries( # Specifies the target library.
    55.                        native-lib opencv-lib
    56.  
    57.                        # Links the target library to the log library
    58.                        # included in the NDK.
    59.                        ${log-lib} )

    3.2修改app下的build.gradle文件 只支持armv7

     同步运行项目至手机设备

    出现如下图所示错误：

     java.lang.UnsatisfiedLinkError: dlopen failed: library "libc++_shared.so" not found

    解决方式如下：

    修改app下的build.gradle文件

     重新同步项目并运行项目至手机设备

    3.3新建FaceDetection类

    FaceDetection内容如下：

    1. package com.suoer.ndk.opencvtestapplication;
    2.  
    3. import android.graphics.Bitmap;
    4.  
    5. public class FaceDetection {
    6.     // Used to load the 'native-lib' library on application startup.
    7.     static {
    8.         System.loadLibrary("native-lib");
    9.     }
    10.     /**
    11.      * 检测人脸并保存人脸信息
    12.      * @param faceBitmap
    13.      */
    14.  
    15.     public native int faceDetectionSaveInfo(Bitmap faceBitmap);
    16.  
    17.     /**
    18.      * 加载人脸识别的分类器文件
    19.      * @param filePath
    20.      */
    21.     public native boolean loadCascade(String filePath);
    22.  
    23.  
    24. }

    3.4修改MainActivity类

    因为需要拍照以及保存图片，所以需要权限处理。这里使用rxpermissions

    rxpermissions的具体使用请参照github链接：GitHub - tbruyelle/RxPermissions: Android runtime permissions powered by RxJava2

    因为保存图片是耗时操作，需要开启子线程完成，所以需要处理线程问题。这里使用rxandroid

    rxandroid的具体使用请参照github链接：GitHub - ReactiveX/RxAndroid: RxJava bindings for Android

    修改app下的build.gradle文件

     app下的build.gradle文件内容：

    1. plugins {
    2.     id 'com.android.application'
    3. }
    4.  
    5. android {
    6.     compileSdkVersion 32
    7.     buildToolsVersion "32.0.0"
    8.  
    9.     defaultConfig {
    10.         applicationId "com.suoer.ndk.opencvtestapplication"
    11.         minSdkVersion 16
    12.         targetSdkVersion 32
    13.         versionCode 1
    14.         versionName "1.0"
    15.  
    16.         testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
    17.         externalNativeBuild {
    18.             cmake {
    19.                 cppFlags "-std=c++11 -Wno-nonportable-include-path -Wno-deprecated-register -Wno-writable-strings"
    20.                 //远程下载
    21.                 arguments "-DANDROID_STL=c++_shared"
    22.  
    23.             }
    24.         }
    25.         ndk {
    26.             abiFilters("armeabi-v7a")
    27.         }
    28.     }
    29.  
    30.     buildTypes {
    31.         release {
    32.             minifyEnabled false
    33.             proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
    34.         }
    35.     }
    36.     externalNativeBuild {
    37.         cmake {
    38.             path "src/main/cpp/CMakeLists.txt"
    39.             version "3.10.2"
    40.         }
    41.     }
    42.     compileOptions {
    43.         sourceCompatibility JavaVersion.VERSION_1_8
    44.         targetCompatibility JavaVersion.VERSION_1_8
    45.     }
    46. }
    47.  
    48. dependencies {
    49.  
    50.     implementation 'androidx.appcompat:appcompat:1.1.0'
    51.     implementation 'com.google.android.material:material:1.1.0'
    52.     implementation 'androidx.constraintlayout:constraintlayout:1.1.3'
    53.     testImplementation 'junit:junit:4.+'
    54.     androidTestImplementation 'androidx.test.ext:junit:1.1.1'
    55.     androidTestImplementation 'androidx.test.espresso:espresso-core:3.2.0'
    56.     implementation 'com.github.tbruyelle:rxpermissions:0.12'
    57.     implementation 'io.reactivex.rxjava3:rxandroid:3.0.0'
    58. }

    修改项目下的build.gradle文件

     项目下的build.gradle文件内容：

    1. // Top-level build file where you can add configuration options common to all sub-projects/modules.
    2. buildscript {
    3.     repositories {
    4.         google()
    5.         jcenter()
    6.     }
    7.     dependencies {
    8.         classpath "com.android.tools.build:gradle:4.1.0"
    9.  
    10.         // NOTE: Do not place your application dependencies here; they belong
    11.         // in the individual module build.gradle files
    12.     }
    13. }
    14.  
    15. allprojects {
    16.     repositories {
    17.         google()
    18.         jcenter()
    19.         maven { url 'https://jitpack.io' }
    20.         maven { url "https://oss.jfrog.org/libs-snapshot" }
    21.     }
    22. }
    23.  
    24. task clean(type: Delete) {
    25.     delete rootProject.buildDir
    26. }

    修改AndroidManifest.xml添加权限

     

    1.     <uses-permission android:name="android.permission.CAMERA" />
    2.     <uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE"/>
    3.     <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>

    MainActivity类内容如下：

    1. package com.suoer.ndk.opencvtestapplication;
    2.  
    3. import android.Manifest;
    4. import android.content.Context;
    5. import android.content.pm.PackageManager;
    6. import android.graphics.Bitmap;
    7. import android.os.Bundle;
    8. import android.util.Log;
    9. import android.view.SurfaceView;
    10. import android.view.View;
    11. import android.view.Window;
    12. import android.view.WindowManager;
    13. import android.widget.Button;
    14. import android.widget.ImageView;
    15. import android.widget.Toast;
    16.  
    17. import com.suoer.ndk.opencvtestapplication.camerahandle.BitmapInterface;
    18. import com.suoer.ndk.opencvtestapplication.camerahandle.CameraSurfaceHolder;
    19. import com.suoer.ndk.opencvtestapplication.camerahandle.FrontCamera;
    20. import com.suoer.ndk.opencvtestapplication.camerahandle.SaveImageTask;
    21. import com.suoer.ndk.opencvtestapplication.camerahandle.SurfaceViewCallback;
    22. import com.tbruyelle.rxpermissions3.RxPermissions;
    23.  
    24. import java.io.ByteArrayOutputStream;
    25. import java.io.File;
    26. import java.io.FileOutputStream;
    27. import java.io.IOException;
    28. import java.io.InputStream;
    29.  
    30. import androidx.appcompat.app.AppCompatActivity;
    31. import io.reactivex.rxjava3.functions.Consumer;
    32.  
    33. public class MainActivity extends AppCompatActivity {
    34.     private static final String TAG = "MainActivity";
    35.     private SurfaceView mSurfaceView;
    36.     private ImageView faceImg;
    37.     private Button faceDetectionBtn;
    38.  
    39.     private FaceDetection mFaceDetection;
    40.     private File mCascadeFile;
    41.  
    42.     private CameraSurfaceHolder mCameraSurfaceHolder=new CameraSurfaceHolder();
    43.     private SurfaceViewCallback mSurfaceViewCallback;
    44.     private FrontCamera mFrontCamera;
    45.  
    46.  
    47.  
    48.     @Override
    49.     protected void onCreate(Bundle savedInstanceState) {
    50.         super.onCreate(savedInstanceState);
    51.         requestWindowFeature(Window.FEATURE_NO_TITLE);
    52.         getWindow().addFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN);
    53.         initView();
    54.         applyPermission();
    55.         initFaceDetection();
    56.     }
    57.  
    58.     private void initFaceDetection() {
    59.         copyCascadeFile();
    60.         mFaceDetection = new FaceDetection();
    61.         if (mFaceDetection != null) {
    62.             boolean load = mFaceDetection.loadCascade(mCascadeFile.getAbsolutePath());
    63.             if (load) {
    64.                 Toast.makeText(this, "加载分类器文件成功！", Toast.LENGTH_SHORT).show();
    65.             } else {
    66.                 Toast.makeText(this, "加载分类器文件失败！", Toast.LENGTH_SHORT).show();
    67.             }
    68.         }
    69.  
    70.     }
    71.  
    72.     //申请权限
    73.     private void applyPermission() {
    74.         if (!checkCameraHardware(this)) {
    75.             return;
    76.         }
    77.         RxPermissions rxPermissions = new RxPermissions(this);
    78.         rxPermissions.request(Manifest.permission.READ_EXTERNAL_STORAGE, Manifest.permission.WRITE_EXTERNAL_STORAGE, Manifest.permission.CAMERA).subscribe(new Consumer() {
    79.             @Override
    80.             public void accept(Boolean aBoolean) throws Throwable {
    81.                 if (aBoolean) {
    82.                     Log.e(TAG, "accept: " + aBoolean);
    83.                     faceDetectionBtn.setVisibility(View.VISIBLE);
    84.                     mSurfaceView.setVisibility(View.VISIBLE);
    85.                     //权限全部获取
    86.                     initSurfaceViewPreView();
    87.  
    88.  
    89.                 }
    90.  
    91.             }
    92.         });
    93.  
    94.  
    95.     }
    96.  
    97.     private void initSurfaceViewPreView() {
    98.         mCameraSurfaceHolder.setCameraSurfaceHolder(MainActivity.this, mSurfaceView);
    99.         mSurfaceViewCallback = mCameraSurfaceHolder.mSurfaceViewCallback;
    100.         if (mSurfaceViewCallback != null) {
    101.             mFrontCamera = mSurfaceViewCallback.mFrontCamera;
    102.         }
    103.     }
    104.  
    105.     ;
    106.  
    107.     private void initView() {
    108.         setContentView(R.layout.activity_main);
    109.         mSurfaceView = findViewById(R.id.face_surfaceView);
    110.         mSurfaceView.setVisibility(View.GONE);
    111.         faceDetectionBtn = findViewById(R.id.faceDetectionBtn);
    112.         faceImg = findViewById(R.id.faceImg);
    113.         faceDetectionBtn.setOnClickListener(new View.OnClickListener() {
    114.             @Override
    115.             public void onClick(View v) {
    116.                 if (mFrontCamera != null) {
    117.                     //拍照的时候进行人脸识别
    118.                     mFrontCamera.takePicture(new BitmapInterface() {
    119.                         @Override
    120.                         public void setBitMap(Bitmap bitMap) {
    121.                             if(bitMap==null){
    122.                                 Toast.makeText(MainActivity.this,"拍照失败！",Toast.LENGTH_SHORT).show();
    123.                                 return;
    124.                             }
    125.                             //人脸识别
    126.                             int result = mFaceDetection.faceDetectionSaveInfo(bitMap);
    127.                             if (result != 0) {
    128.                                 Toast.makeText(MainActivity.this, "检测人脸失败!", Toast.LENGTH_SHORT).show();
    129.                                 return;
    130.                             }
    131.  
    132.                             faceImg.setVisibility(View.VISIBLE);
    133.                             faceImg.setImageBitmap(bitMap);
    134.                             byte[]data= bitmap2byte(bitMap);
    135.                             //rxandroid实现开启子线程保存文件
    136.                             new SaveImageTask(MainActivity.this,faceImg).saveImage(data);
    137.                             //AsyncTask异步任务实现开启子线程保存文件
    138.                             //new SaveImageAsyncTask(MainActivity.this,faceImg).execute(data);
    139.                         }
    140.                     });
    141.                 }
    142.  
    143.  
    144.             }
    145.         });
    146.  
    147.     }
    148.     private byte[] bitmap2byte(Bitmap photoBitmap){
    149.         创建对应的流对象
    150.         ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream();
    151.         photoBitmap.compress(Bitmap.CompressFormat.JPEG,100,byteArrayOutputStream);//将流对象与Bitmap对象进行关联。
    152.         byte [] array=byteArrayOutputStream.toByteArray();//使用流对象，将Bitmap对象转换为byte[]数组
    153.         return array;
    154.  
    155.     }
    156.  
    157.  
    158.  
    159.  
    160.     private void copyCascadeFile() {
    161.  
    162.         try {
    163.             // load cascade file from application resources
    164.             InputStream is = getResources().openRawResource(R.raw.lbpcascade_frontalface);
    165.             File cascadeDir = getDir("cascade", Context.MODE_PRIVATE);
    166.             mCascadeFile = new File(cascadeDir, "lbpcascade_frontalface.xml");
    167.             if (mCascadeFile.exists()) return;
    168.             FileOutputStream os = new FileOutputStream(mCascadeFile);
    169.  
    170.             byte[] buffer = new byte[4096];
    171.             int bytesRead;
    172.             while ((bytesRead = is.read(buffer)) != -1) {
    173.                 os.write(buffer, 0, bytesRead);
    174.             }
    175.             is.close();
    176.             os.close();
    177.             cascadeDir.delete();
    178.  
    179.         } catch (IOException e) {
    180.             e.printStackTrace();
    181.             Log.e(TAG, "Failed to load cascade. Exception thrown: " + e);
    182.         }
    183.     }
    184.  
    185.     /**
    186.      * 检测是否存在摄像头
    187.      *
    188.      * @param context
    189.      * @return
    190.      */
    191.     private boolean checkCameraHardware(Context context) {
    192.         if (context.getPackageManager().hasSystemFeature(PackageManager.FEATURE_CAMERA)) {
    193.             return true;
    194.         } else {
    195.             Toast.makeText(this, "不具备摄像头硬件", Toast.LENGTH_SHORT).show();
    196.             return false;
    197.         }
    198.     }
    199.  
    200. }


    布局activity_main.xml

    1. "1.0" encoding="utf-8"?>
    2. <androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    3.     xmlns:app="http://schemas.android.com/apk/res-auto"
    4.     xmlns:tools="http://schemas.android.com/tools"
    5.     android:layout_width="match_parent"
    6.     android:layout_height="match_parent"
    7.     tools:context=".MainActivity">
    8.     <SurfaceView
    9.         app:layout_constraintTop_toTopOf="@+id/faceDetectionBtn"
    10.         android:id="@+id/face_surfaceView"
    11.         android:layout_width="match_parent"
    12.         android:layout_height="match_parent"/>
    13.     <ImageView
    14.         app:layout_constraintTop_toTopOf="@+id/faceDetectionBtn"
    15.         android:visibility="gone"
    16.         android:id="@+id/faceImg"
    17.         android:src="@drawable/face"
    18.         android:layout_width="match_parent"
    19.         android:layout_height="match_parent">ImageView>
    20.     <Button
    21.         android:visibility="gone"
    22.         android:id="@+id/faceDetectionBtn"
    23.         android:layout_width="match_parent"
    24.         android:layout_height="wrap_content"
    25.         android:text="人脸识别"
    26.         app:layout_constraintBottom_toBottomOf="parent"
    27.         app:layout_constraintLeft_toLeftOf="parent"
    28.         app:layout_constraintRight_toRightOf="parent"
    29.          />
    30.  
    31. androidx.constraintlayout.widget.ConstraintLayout>

    3.5修改native-lib.cpp

    1. #include 
    2. #include 
    3. #include 
    4. #include 
    5. #include 
    6. #include 
    7.  
    8. #define TAG "JNI_LOG"
    9. #define LOGE(...)__android_log_print(ANDROID_LOG_ERROR,TAG,__VA_ARGS__)
    10. using namespace cv;
    11. CascadeClassifier cascadeClassifier;
    12.  
    13.  
    14. //使用命名空间
    15. void bitmap2Mat(JNIEnv *env, Mat &mat, jobject bitmap);
    16.  
    17. //mat转成bitmap
    18. void mat2Bitmap(JNIEnv *env, Mat mat, jobject bitmap);
    19.  
    20. //bitmap转成mat
    21. void bitmap2Mat(JNIEnv *env, Mat &mat, jobject bitmap) {
    22. //Mat里面有个type:CV_8UC4 刚好对上bitmap中的ARGB_8888 CV_8UC2 刚好匹配bitmap中的RGB_565
    23. //1.获取bitmap信息
    24. AndroidBitmapInfo info;
    25. void *pixels;
    26. AndroidBitmap_getInfo(env,bitmap,&info);
    27.  
    28. //锁定bitmap画布
    29. AndroidBitmap_lockPixels(env,bitmap,&pixels);
    30. //指定mat的宽高和type BGRA
    31. mat.create(info.height,info.width,CV_8UC4);
    32.  
    33. if(info.format==ANDROID_BITMAP_FORMAT_RGBA_8888){
    34. //对应的mat应该是CV_8UC4
    35. Mat temp(info.height,info.width,CV_8UC4,pixels);
    36. //把数据temp复制到mat里面
    37. temp.copyTo(mat);
    38.  
    39. }else if(info.format==ANDROID_BITMAP_FORMAT_RGB_565){
    40.     //对应的mat应该是CV_8UC2
    41.     Mat temp(info.height,info.width,CV_8UC2,pixels);
    42.     //上面mat创建的是CV_8UC4 要改为CV_8UC2  CV_8UC2数据拷贝到CV_8UC4
    43.     cvtColor(temp,mat,COLOR_BGR5652BGRA);
    44. }
    45. //其他需要自己去转
    46. //解锁画布
    47. AndroidBitmap_unlockPixels(env,bitmap);
    48. }
    49.  
    50. extern "C"
    51. JNIEXPORT jint JNICALL
    52. Java_com_suoer_ndk_opencvtestapplication_FaceDetection_faceDetectionSaveInfo(JNIEnv *env,
    53.                                                                              jobject thiz,
    54.                                                                              jobject face_bitmap) {
    55.     // TODO: implement faceDetectionSaveInfo()
    56.     //检测人脸 opencv有关键的类是Mat,opencv是c和c++写的，只会处理Mat,android里面是Bitmap
    57.     //1.Bitmap转成opencv能操作的c++对象 Mat ,Mat是一个矩阵
    58.     Mat mat;
    59.     bitmap2Mat(env,mat,face_bitmap);
    60.     //处理灰度opencv 处理灰度图 提高效率,一般所有的操作都会对齐进行处理
    61.     Mat gray_mat;
    62.     cvtColor(mat,gray_mat,COLOR_BGRA2GRAY);
    63.  
    64.     //再次处理直方均衡补偿
    65.     Mat equalize_mat;
    66.     equalizeHist(gray_mat,equalize_mat);
    67.     //识别人脸 当然我们可以直接用彩色图去做，识别人脸要加载人脸分类器文件
    68.     std::vector faces;
    69.     cascadeClassifier.detectMultiScale(equalize_mat,faces,1.1,5);
    70.     LOGE("人脸个数:%d",faces.size());
    71.     if(faces.size()!=1){
    72.         return -1;
    73.     }
    74.  
    75.         Rect faceRect=faces[0];
    76.         //在人脸部分画个图
    77.         rectangle(mat,faceRect,Scalar(255,155,155),8);
    78.         //把mat 放到bitmap中 图片展示出来
    79.         //mat2Bitmap(env,mat,face_bitmap);
    80.         //保存人脸信息 Mat,图片
    81.         Mat face_info_mat(equalize_mat,faceRect);
    82.         //保存face_info_mat
    83.         mat2Bitmap(env,face_info_mat,face_bitmap);
    84.         //mat2Bitmap(env,equalize_mat,face_bitmap);
    85.  
    86.  
    87.  
    88.  
    89.  
    90.  
    91.  
    92.     //保存人脸信息
    93.     return 0;
    94. }
    95.  
    96. void mat2Bitmap(JNIEnv *env, Mat mat, jobject bitmap) {
    97. //Mat里面有个type:CV_8UC4 刚好对上bitmap中的ARGB_8888 CV_8UC2 刚好匹配bitmap中的RGB_565
    98. //1.获取bitmap信息
    99.     AndroidBitmapInfo info;
    100.     void *pixels;
    101.     AndroidBitmap_getInfo(env,bitmap,&info);
    102.  
    103. //锁定bitmap画布
    104.     AndroidBitmap_lockPixels(env,bitmap,&pixels);
    105.  
    106.  
    107.     if(info.format==ANDROID_BITMAP_FORMAT_RGBA_8888){
    108. //对应的mat应该是CV_8UC4
    109.         Mat temp(info.height,info.width,CV_8UC4,pixels);
    110.         if(mat.type()==CV_8UC4){
    111.             mat.copyTo(temp);
    112.         }else if(mat.type()==CV_8UC2){
    113.             cvtColor(mat,temp,COLOR_BGR5652BGRA);
    114.         }
    115.         else if(mat.type()==CV_8UC1){//灰度mat
    116.             cvtColor(mat,temp,COLOR_GRAY2BGRA);
    117.         }
    118.     }else if(info.format==ANDROID_BITMAP_FORMAT_RGB_565){
    119.         //对应的mat应该是CV_8UC2
    120.         Mat temp(info.height,info.width,CV_8UC2,pixels);
    121.         if(mat.type()==CV_8UC4){
    122.             cvtColor(mat,temp,COLOR_BGRA2BGR565);
    123.         }else if(mat.type()==CV_8UC2){
    124.             mat.copyTo(temp);
    125.         }
    126.         else if(mat.type()==CV_8UC1){//灰度mat
    127.             cvtColor(mat,temp,COLOR_GRAY2BGR565);
    128.         }
    129.  
    130.     }
    131. //其他需要自己去转
    132. //解锁画布
    133.     AndroidBitmap_unlockPixels(env,bitmap);
    134. }
    135.  
    136. extern "C"
    137. JNIEXPORT jboolean JNICALL
    138. Java_com_suoer_ndk_opencvtestapplication_FaceDetection_loadCascade(JNIEnv *env, jobject thiz,
    139.                                                                    jstring file_path) {
    140.     // TODO: implement loadCascade()
    141.     const char *filePath=env->GetStringUTFChars(file_path,0);
    142.     bool load=cascadeClassifier.load(filePath);
    143.     env->ReleaseStringUTFChars(file_path,filePath);
    144.     return load;
    145. }

    运行app至手机设备出现如下图所示错误

    error: undefined reference to 'AndroidBitmap_getInfo'

     解决方式修改CMakeLists.txt

     

    1. target_link_libraries( # Specifies the target library.
    2.                        native-lib opencv-lib
    3.                        #加入该依赖库
    4.                        jnigraphics
    5.  
    6.                        # Links the target library to the log library
    7.                        # included in the NDK.
    8.                        ${log-lib} )

    CMakeLists.txt内容如下：

    1. # For more information about using CMake with Android Studio, read the
    2. # documentation: https://d.android.com/studio/projects/add-native-code.html
    3.  
    4. # Sets the minimum version of CMake required to build the native library.
    5.  
    6. cmake_minimum_required(VERSION 3.10.2)
    7.  
    8. # Declares and names the project.
    9.  
    10. project("opencvtestapplication")
    11. #需要引入我们头文件，以这个配置的目录为基准
    12. include_directories(${CMAKE_SOURCE_DIR}/../jni/include)
    13.  
    14. # Creates and names a library, sets it as either STATIC
    15. # or SHARED, and provides the relative paths to its source code.
    16. # You can define multiple libraries, and CMake builds them for you.
    17. # Gradle automatically packages shared libraries with your APK.
    18.  
    19. add_library( # Sets the name of the library.
    20.              native-lib
    21.  
    22.              # Sets the library as a shared library.
    23.              SHARED
    24.  
    25.              # Provides a relative path to your source file(s).
    26.              native-lib.cpp )
    27. # 添加opencv的库
    28. add_library(
    29.         opencv-lib
    30.         SHARED
    31.         IMPORTED)
    32. set_target_properties(
    33.         opencv-lib
    34.         PROPERTIES IMPORTED_LOCATION
    35.         ${CMAKE_SOURCE_DIR}/../jni/armeabi-v7a/libopencv_java4.so)
    36.  
    37. # Searches for a specified prebuilt library and stores the path as a
    38. # variable. Because CMake includes system libraries in the search path by
    39. # default, you only need to specify the name of the public NDK library
    40. # you want to add. CMake verifies that the library exists before
    41. # completing its build.
    42.  
    43. find_library( # Sets the name of the path variable.
    44.               log-lib
    45.  
    46.               # Specifies the name of the NDK library that
    47.               # you want CMake to locate.
    48.               log )
    49.  
    50. # Specifies libraries CMake should link to your target library. You
    51. # can link multiple libraries, such as libraries you define in this
    52. # build script, prebuilt third-party libraries, or system libraries.
    53.  
    54. target_link_libraries( # Specifies the target library.
    55.                        native-lib opencv-lib
    56.                        #加入该依赖库
    57.                        jnigraphics
    58.  
    59.                        # Links the target library to the log library
    60.                        # included in the NDK.
    61.                        ${log-lib} )

    其他详细内容可见Demo。

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  • 原文地址：https://blog.csdn.net/Jushuzhan/article/details/126619177