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：

# 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 3.10.2)# Declares and names the project.project("opencvtestapplication")
#需要引入我们头文件，以这个配置的目录为基准
include_directories(${CMAKE_SOURCE_DIR}/../jni/include)# Creates and names a library, sets it as either STATIC
# or SHARED, and provides the relative paths to its source code.
# You can define multiple libraries, and CMake builds them for you.
# Gradle automatically packages shared libraries with your APK.add_library( # Sets the name of the library.native-lib# Sets the library as a shared library.SHARED# Provides a relative path to your source file(s).native-lib.cpp )
# 添加opencv的库
add_library(opencv-libSHAREDIMPORTED)
set_target_properties(opencv-libPROPERTIES IMPORTED_LOCATION${CMAKE_SOURCE_DIR}/../jni/armeabi-v7a/libopencv_java4.so)# 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-lib# Links the target library to the log library# included in the NDK.${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：

package com.suoer.ndk.opencvtestapplication;import android.graphics.Bitmap;public class FaceDetection {// Used to load the 'native-lib' library on application startup.static {System.loadLibrary("native-lib");}/*** 检测人脸并保存人脸信息* @param faceBitmap*/public native int faceDetectionSaveInfo(Bitmap faceBitmap);/*** 加载人脸识别的分类器文件* @param filePath*/public native boolean loadCascade(String filePath);}

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：

plugins {id 'com.android.application'
}android {compileSdkVersion 32buildToolsVersion "32.0.0"defaultConfig {applicationId "com.suoer.ndk.opencvtestapplication"minSdkVersion 16targetSdkVersion 32versionCode 1versionName "1.0"testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"externalNativeBuild {cmake {cppFlags "-std=c++11 -Wno-nonportable-include-path -Wno-deprecated-register -Wno-writable-strings"//远程下载arguments "-DANDROID_STL=c++_shared"}}ndk {abiFilters("armeabi-v7a")}}buildTypes {release {minifyEnabled falseproguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'}}externalNativeBuild {cmake {path "src/main/cpp/CMakeLists.txt"version "3.10.2"}}compileOptions {sourceCompatibility JavaVersion.VERSION_1_8targetCompatibility JavaVersion.VERSION_1_8}
}dependencies {implementation 'androidx.appcompat:appcompat:1.1.0'implementation 'com.google.android.material:material:1.1.0'implementation 'androidx.constraintlayout:constraintlayout:1.1.3'testImplementation 'junit:junit:4.+'androidTestImplementation 'androidx.test.ext:junit:1.1.1'androidTestImplementation 'androidx.test.espresso:espresso-core:3.2.0'implementation 'com.github.tbruyelle:rxpermissions:0.12'implementation 'io.reactivex.rxjava3:rxandroid:3.0.0'
}

修改项目下的build.gradle文件

项目下的build.gradle文件内容：

// Top-level build file where you can add configuration options common to all sub-projects/modules.
buildscript {repositories {google()jcenter()}dependencies {classpath "com.android.tools.build:gradle:4.1.0"// NOTE: Do not place your application dependencies here; they belong// in the individual module build.gradle files}
}allprojects {repositories {google()jcenter()maven { url 'https://jitpack.io' }maven { url "https://oss.jfrog.org/libs-snapshot" }}
}task clean(type: Delete) {delete rootProject.buildDir
}

修改AndroidManifest.xml添加权限

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

MainActivity类内容如下：

package com.suoer.ndk.opencvtestapplication;import android.Manifest;
import android.content.Context;
import android.content.pm.PackageManager;
import android.graphics.Bitmap;
import android.os.Bundle;
import android.util.Log;
import android.view.SurfaceView;
import android.view.View;
import android.view.Window;
import android.view.WindowManager;
import android.widget.Button;
import android.widget.ImageView;
import android.widget.Toast;import com.suoer.ndk.opencvtestapplication.camerahandle.BitmapInterface;
import com.suoer.ndk.opencvtestapplication.camerahandle.CameraSurfaceHolder;
import com.suoer.ndk.opencvtestapplication.camerahandle.FrontCamera;
import com.suoer.ndk.opencvtestapplication.camerahandle.SaveImageTask;
import com.suoer.ndk.opencvtestapplication.camerahandle.SurfaceViewCallback;
import com.tbruyelle.rxpermissions3.RxPermissions;import java.io.ByteArrayOutputStream;
import java.io.File;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;import androidx.appcompat.app.AppCompatActivity;
import io.reactivex.rxjava3.functions.Consumer;public class MainActivity extends AppCompatActivity {private static final String TAG = "MainActivity";private SurfaceView mSurfaceView;private ImageView faceImg;private Button faceDetectionBtn;private FaceDetection mFaceDetection;private File mCascadeFile;private CameraSurfaceHolder mCameraSurfaceHolder=new CameraSurfaceHolder();private SurfaceViewCallback mSurfaceViewCallback;private FrontCamera mFrontCamera;@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);requestWindowFeature(Window.FEATURE_NO_TITLE);getWindow().addFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN);initView();applyPermission();initFaceDetection();}private void initFaceDetection() {copyCascadeFile();mFaceDetection = new FaceDetection();if (mFaceDetection != null) {boolean load = mFaceDetection.loadCascade(mCascadeFile.getAbsolutePath());if (load) {Toast.makeText(this, "加载分类器文件成功！", Toast.LENGTH_SHORT).show();} else {Toast.makeText(this, "加载分类器文件失败！", Toast.LENGTH_SHORT).show();}}}//申请权限private void applyPermission() {if (!checkCameraHardware(this)) {return;}RxPermissions rxPermissions = new RxPermissions(this);rxPermissions.request(Manifest.permission.READ_EXTERNAL_STORAGE, Manifest.permission.WRITE_EXTERNAL_STORAGE, Manifest.permission.CAMERA).subscribe(new Consumer<Boolean>() {@Overridepublic void accept(Boolean aBoolean) throws Throwable {if (aBoolean) {Log.e(TAG, "accept: " + aBoolean);faceDetectionBtn.setVisibility(View.VISIBLE);mSurfaceView.setVisibility(View.VISIBLE);//权限全部获取initSurfaceViewPreView();}}});}private void initSurfaceViewPreView() {mCameraSurfaceHolder.setCameraSurfaceHolder(MainActivity.this, mSurfaceView);mSurfaceViewCallback = mCameraSurfaceHolder.mSurfaceViewCallback;if (mSurfaceViewCallback != null) {mFrontCamera = mSurfaceViewCallback.mFrontCamera;}};private void initView() {setContentView(R.layout.activity_main);mSurfaceView = findViewById(R.id.face_surfaceView);mSurfaceView.setVisibility(View.GONE);faceDetectionBtn = findViewById(R.id.faceDetectionBtn);faceImg = findViewById(R.id.faceImg);faceDetectionBtn.setOnClickListener(new View.OnClickListener() {@Overridepublic void onClick(View v) {if (mFrontCamera != null) {//拍照的时候进行人脸识别mFrontCamera.takePicture(new BitmapInterface() {@Overridepublic void setBitMap(Bitmap bitMap) {if(bitMap==null){Toast.makeText(MainActivity.this,"拍照失败！",Toast.LENGTH_SHORT).show();return;}//人脸识别int result = mFaceDetection.faceDetectionSaveInfo(bitMap);if (result != 0) {Toast.makeText(MainActivity.this, "检测人脸失败!", Toast.LENGTH_SHORT).show();return;}faceImg.setVisibility(View.VISIBLE);faceImg.setImageBitmap(bitMap);byte[]data= bitmap2byte(bitMap);//rxandroid实现开启子线程保存文件new SaveImageTask(MainActivity.this,faceImg).saveImage(data);//AsyncTask异步任务实现开启子线程保存文件//new SaveImageAsyncTask(MainActivity.this,faceImg).execute(data);}});}}});}private byte[] bitmap2byte(Bitmap photoBitmap){创建对应的流对象ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream();photoBitmap.compress(Bitmap.CompressFormat.JPEG,100,byteArrayOutputStream);//将流对象与Bitmap对象进行关联。byte [] array=byteArrayOutputStream.toByteArray();//使用流对象，将Bitmap对象转换为byte[]数组return array;}private void copyCascadeFile() {try {// load cascade file from application resourcesInputStream is = getResources().openRawResource(R.raw.lbpcascade_frontalface);File cascadeDir = getDir("cascade", Context.MODE_PRIVATE);mCascadeFile = new File(cascadeDir, "lbpcascade_frontalface.xml");if (mCascadeFile.exists()) return;FileOutputStream os = new FileOutputStream(mCascadeFile);byte[] buffer = new byte[4096];int bytesRead;while ((bytesRead = is.read(buffer)) != -1) {os.write(buffer, 0, bytesRead);}is.close();os.close();cascadeDir.delete();} catch (IOException e) {e.printStackTrace();Log.e(TAG, "Failed to load cascade. Exception thrown: " + e);}}/*** 检测是否存在摄像头** @param context* @return*/private boolean checkCameraHardware(Context context) {if (context.getPackageManager().hasSystemFeature(PackageManager.FEATURE_CAMERA)) {return true;} else {Toast.makeText(this, "不具备摄像头硬件", Toast.LENGTH_SHORT).show();return false;}}}

布局activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"xmlns:app="http://schemas.android.com/apk/res-auto"xmlns:tools="http://schemas.android.com/tools"android:layout_width="match_parent"android:layout_height="match_parent"tools:context=".MainActivity"><SurfaceViewapp:layout_constraintTop_toTopOf="@+id/faceDetectionBtn"android:id="@+id/face_surfaceView"android:layout_width="match_parent"android:layout_height="match_parent"/><ImageViewapp:layout_constraintTop_toTopOf="@+id/faceDetectionBtn"android:visibility="gone"android:id="@+id/faceImg"android:src="@drawable/face"android:layout_width="match_parent"android:layout_height="match_parent"></ImageView><Buttonandroid:visibility="gone"android:id="@+id/faceDetectionBtn"android:layout_width="match_parent"android:layout_height="wrap_content"android:text="人脸识别"app:layout_constraintBottom_toBottomOf="parent"app:layout_constraintLeft_toLeftOf="parent"app:layout_constraintRight_toRightOf="parent"/></androidx.constraintlayout.widget.ConstraintLayout>

3.5修改native-lib.cpp

#include <jni.h>
#include <string>
#include <opencv2/opencv.hpp>
#include <android/bitmap.h>
#include <android/log.h>
#include <opencv2/imgcodecs/legacy/constants_c.h>#define TAG "JNI_LOG"
#define LOGE(...)__android_log_print(ANDROID_LOG_ERROR,TAG,__VA_ARGS__)
using namespace cv;
CascadeClassifier cascadeClassifier;//使用命名空间
void bitmap2Mat(JNIEnv *env, Mat &mat, jobject bitmap);//mat转成bitmap
void mat2Bitmap(JNIEnv *env, Mat mat, jobject bitmap);//bitmap转成mat
void bitmap2Mat(JNIEnv *env, Mat &mat, jobject bitmap) {
//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
//1.获取bitmap信息
AndroidBitmapInfo info;
void *pixels;
AndroidBitmap_getInfo(env,bitmap,&info);//锁定bitmap画布
AndroidBitmap_lockPixels(env,bitmap,&pixels);
//指定mat的宽高和type BGRA
mat.create(info.height,info.width,CV_8UC4);if(info.format==ANDROID_BITMAP_FORMAT_RGBA_8888){
//对应的mat应该是CV_8UC4
Mat temp(info.height,info.width,CV_8UC4,pixels);
//把数据temp复制到mat里面
temp.copyTo(mat);}else if(info.format==ANDROID_BITMAP_FORMAT_RGB_565){//对应的mat应该是CV_8UC2Mat temp(info.height,info.width,CV_8UC2,pixels);//上面mat创建的是CV_8UC4 要改为CV_8UC2  CV_8UC2数据拷贝到CV_8UC4cvtColor(temp,mat,COLOR_BGR5652BGRA);
}
//其他需要自己去转
//解锁画布
AndroidBitmap_unlockPixels(env,bitmap);
}extern "C"
JNIEXPORT jint JNICALL
Java_com_suoer_ndk_opencvtestapplication_FaceDetection_faceDetectionSaveInfo(JNIEnv *env,jobject thiz,jobject face_bitmap) {// TODO: implement faceDetectionSaveInfo()//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//1.Bitmap转成opencv能操作的c++对象 Mat ,Mat是一个矩阵Mat mat;bitmap2Mat(env,mat,face_bitmap);//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Mat gray_mat;cvtColor(mat,gray_mat,COLOR_BGRA2GRAY);//再次处理直方均衡补偿Mat equalize_mat;equalizeHist(gray_mat,equalize_mat);//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std::vector<Rect> faces;cascadeClassifier.detectMultiScale(equalize_mat,faces,1.1,5);LOGE("人脸个数:%d",faces.size());if(faces.size()!=1){return -1;}Rect faceRect=faces[0];//在人脸部分画个图rectangle(mat,faceRect,Scalar(255,155,155),8);//把mat 放到bitmap中 图片展示出来//mat2Bitmap(env,mat,face_bitmap);//保存人脸信息 Mat,图片Mat face_info_mat(equalize_mat,faceRect);//保存face_info_matmat2Bitmap(env,face_info_mat,face_bitmap);//mat2Bitmap(env,equalize_mat,face_bitmap);//保存人脸信息return 0;
}void mat2Bitmap(JNIEnv *env, Mat mat, jobject bitmap) {
//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
//1.获取bitmap信息AndroidBitmapInfo info;void *pixels;AndroidBitmap_getInfo(env,bitmap,&info);//锁定bitmap画布AndroidBitmap_lockPixels(env,bitmap,&pixels);if(info.format==ANDROID_BITMAP_FORMAT_RGBA_8888){
//对应的mat应该是CV_8UC4Mat temp(info.height,info.width,CV_8UC4,pixels);if(mat.type()==CV_8UC4){mat.copyTo(temp);}else if(mat.type()==CV_8UC2){cvtColor(mat,temp,COLOR_BGR5652BGRA);}else if(mat.type()==CV_8UC1){//灰度matcvtColor(mat,temp,COLOR_GRAY2BGRA);}}else if(info.format==ANDROID_BITMAP_FORMAT_RGB_565){//对应的mat应该是CV_8UC2Mat temp(info.height,info.width,CV_8UC2,pixels);if(mat.type()==CV_8UC4){cvtColor(mat,temp,COLOR_BGRA2BGR565);}else if(mat.type()==CV_8UC2){mat.copyTo(temp);}else if(mat.type()==CV_8UC1){//灰度matcvtColor(mat,temp,COLOR_GRAY2BGR565);}}
//其他需要自己去转
//解锁画布AndroidBitmap_unlockPixels(env,bitmap);
}extern "C"
JNIEXPORT jboolean JNICALL
Java_com_suoer_ndk_opencvtestapplication_FaceDetection_loadCascade(JNIEnv *env, jobject thiz,jstring file_path) {// TODO: implement loadCascade()const char *filePath=env->GetStringUTFChars(file_path,0);bool load=cascadeClassifier.load(filePath);env->ReleaseStringUTFChars(file_path,filePath);return load;
}

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

target_link_libraries( # Specifies the target library.native-lib opencv-lib#加入该依赖库jnigraphics# Links the target library to the log library# included in the NDK.${log-lib} )

CMakeLists.txt内容如下：

# 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 3.10.2)# Declares and names the project.project("opencvtestapplication")
#需要引入我们头文件，以这个配置的目录为基准
include_directories(${CMAKE_SOURCE_DIR}/../jni/include)# Creates and names a library, sets it as either STATIC
# or SHARED, and provides the relative paths to its source code.
# You can define multiple libraries, and CMake builds them for you.
# Gradle automatically packages shared libraries with your APK.add_library( # Sets the name of the library.native-lib# Sets the library as a shared library.SHARED# Provides a relative path to your source file(s).native-lib.cpp )
# 添加opencv的库
add_library(opencv-libSHAREDIMPORTED)
set_target_properties(opencv-libPROPERTIES IMPORTED_LOCATION${CMAKE_SOURCE_DIR}/../jni/armeabi-v7a/libopencv_java4.so)# 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-lib#加入该依赖库jnigraphics# Links the target library to the log library# included in the NDK.${log-lib} )

其他详细内容可见Demo。