android OpenCV研究之动态人脸识别

随着直播渐渐的火起来，像抱着直播大腿的其他功能也渐渐的火起来了，比如说人脸识别。说起人脸识别用处甚广，比如说有以这个功能为核心的app：美颜相机、美图秀秀、SNOW等等，但是美颜相机和美图秀秀是用的国内SDK《Face++》来做的，这个sdk呢好像是他们自己的后台进行识别并不是app本身做识别。这样就跟我们今天要了解的动态识别不是很对路，肯定不能拿到摄像头的一帧画面去调一次接口再接回参数吧，这样性能肯定不行。所以今天就拿SNOW的例子来说，虽然我不知道他是用什么做的，但是我们可以用openCV也能实现。

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我们先看看效果图：

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实现步骤如下：

1、首先我们需要去openCV的官网下载sdk，这个是地址：http://opencv.org/downloads.html

2、然后新建个项目我这里以studio里为基准，在main目录里面新建jniLibs文件夹，为什么叫jniLibs呢，因为这是调用c库的默认文件夹命名，当然你也可以命名其他的，但是需要在build里面指定这个文件夹。好了，打开我们刚才下载的文件，然后一次打开sdk\native\libs，最后把libs目录里面的所有文件夹拷贝到jniLibs里面去。请看图：

3、加好jniLibs之后呢还需要导入一个module，在studio里面点击file->new->import module->导入module目录是刚才下载的sdk\java这个目录。请看图：

4、导入之后呢右键项目打开open module setting选项，在app选项里点击Dependencies这个，然后点击最右边的+号把刚刚导入的module加进去。请看图：

5、现在开始写代码了，这里我把需要写的代码文件会一一贴出来，下面请看图：

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首先是MainActivity的代码：

package com.wyw.facedemo;

import android.content.Context;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.util.Log;
import android.view.View;
import android.view.WindowManager;
import android.widget.Button;
import android.widget.RelativeLayout;

import org.opencv.android.CameraBridgeViewBase;
import org.opencv.android.JavaCameraView;
import org.opencv.android.OpenCVLoader;
import org.opencv.core.Core;
import org.opencv.core.CvType;
import org.opencv.core.Mat;
import org.opencv.core.MatOfRect;
import org.opencv.core.Rect;
import org.opencv.core.Scalar;
import org.opencv.core.Size;
import org.opencv.objdetect.CascadeClassifier;

import java.io.File;
import java.io.FileOutputStream;
import java.io.InputStream;

public class MainActivity extends AppCompatActivity
        implements CameraBridgeViewBase.CvCameraViewListener {

    private CameraBridgeViewBase openCvCameraView;
    private CascadeClassifier cascadeClassifier;
    //图像人脸小于高度的多少就不检测
    private int absoluteFaceSize;
    //临时图像对象
    private Mat matLin;
    //最终图像对象
    private Mat mat;

    //前置摄像头
    public static int CAMERA_FRONT = 0;
    //后置摄像头
    public static int CAMERA_BACK = 1;

    private int camera_scene = CAMERA_BACK;

    private void initializeOpenCVDependencies() {
        try {
            // Copy the resource into a temp file so OpenCV can load it
            InputStream is = getResources().openRawResource(R.raw.lbpcascade_frontalface);
            File cascadeDir = getDir("cascade", Context.MODE_PRIVATE);
            File mCascadeFile = new File(cascadeDir, "lbpcascade_frontalface.xml");
            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();


            // Load the cascade classifier
            cascadeClassifier = new CascadeClassifier(mCascadeFile.getAbsolutePath());
        } catch (Exception e) {
            Log.e("OpenCVActivity", "Error loading cascade", e);
        }


        // And we are ready to go
        openCvCameraView.enableView();
    }


    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        getWindow().addFlags(WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON);
        setContentView(R.layout.activity_main);

        final RelativeLayout relativeLayout = (RelativeLayout) findViewById(R.id.relative);

        openCvCameraView = new JavaCameraView(this, CameraBridgeViewBase.CAMERA_ID_FRONT);
        openCvCameraView.setCvCameraViewListener(this);

        final Button button = new Button(MainActivity.this);
        button.setText("切换摄像头");
        button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                if (camera_scene == CAMERA_FRONT) {//如果是前置摄像头就切换成后置

                    relativeLayout.removeAllViews();
                    openCvCameraView.disableView();
                    openCvCameraView = null;
                    cascadeClassifier = null;

                    openCvCameraView = new JavaCameraView(MainActivity.this, CameraBridgeViewBase.CAMERA_ID_BACK);
                    openCvCameraView.setCvCameraViewListener(MainActivity.this);

                    openCvCameraView.setCameraIndex(CameraBridgeViewBase.CAMERA_ID_BACK);//后置摄像头
                    camera_scene = CAMERA_BACK;

                    relativeLayout.addView(openCvCameraView);
                    relativeLayout.addView(button);

                    initializeOpenCVDependencies();
                } else {

                    relativeLayout.removeAllViews();
                    openCvCameraView.disableView();
                    openCvCameraView = null;
                    cascadeClassifier = null;

                    openCvCameraView = new JavaCameraView(MainActivity.this, CameraBridgeViewBase.CAMERA_ID_FRONT);
                    openCvCameraView.setCvCameraViewListener(MainActivity.this);

                    openCvCameraView.setCameraIndex(CameraBridgeViewBase.CAMERA_ID_FRONT);//前置摄像头
                    camera_scene = CAMERA_FRONT;

                    relativeLayout.addView(openCvCameraView);
                    relativeLayout.addView(button);

                    initializeOpenCVDependencies();
                }
            }
        });

        relativeLayout.addView(openCvCameraView);
        relativeLayout.addView(button);

        if (camera_scene == CAMERA_FRONT) {
            openCvCameraView.setCameraIndex(CameraBridgeViewBase.CAMERA_ID_FRONT);//前置摄像头
        } else if (camera_scene == CAMERA_BACK) {
            openCvCameraView.setCameraIndex(CameraBridgeViewBase.CAMERA_ID_BACK);//后置摄像头
        }
    }

    @Override
    public void onCameraViewStarted(int width, int height) {
        matLin = new Mat(height, width, CvType.CV_8UC4);//临时图像

        // 人脸小于高度的百分之30就不检测
        absoluteFaceSize = (int) (height * 0.3);
    }


    @Override
    public void onCameraViewStopped() {
    }


    @Override
    public Mat onCameraFrame(Mat aInputFrame) {
        //转置函数,将图像翻转（顺时针90度）
        Core.transpose(aInputFrame, matLin);

        if (camera_scene == CAMERA_FRONT) {//前置摄像头
            //转置函数,将图像翻转（对换）
            Core.flip(matLin, aInputFrame, 1);
            //转置函数,将图像顺时针顺转（对换）
            Core.flip(aInputFrame, matLin, 0);
            mat = matLin;
        } else if (camera_scene == CAMERA_BACK) {//后置摄像头
            //转置函数,将图像翻转（对换）
            Core.flip(matLin, aInputFrame, 1);
            mat = aInputFrame;
        }

        MatOfRect faces = new MatOfRect();

        Log.i("123456", "absoluteFaceSize = " + absoluteFaceSize);
        // Use the classifier to detect faces
        if (cascadeClassifier != null) {
            cascadeClassifier.detectMultiScale(mat, faces, 1.1, 1, 1,
                    new Size(absoluteFaceSize, absoluteFaceSize), new Size());
        }


        // 检测出多少个
        Rect[] facesArray = faces.toArray();
        for (int i = 0; i < facesArray.length; i++) {
            Log.i("123456", "facesArray[i].tl()坐上坐标 == " + facesArray[i].tl() + "      facesArray[i].br() == 右下坐标" + facesArray[i].br());
            Core.rectangle(mat, facesArray[i].tl(), facesArray[i].br(), new Scalar(0, 255, 0, 255), 3);
        }

        return mat;
    }


    @Override
    public void onResume() {
        super.onResume();

        if (!OpenCVLoader.initDebug()) {
            Log.e("log_wons", "OpenCV init error");
            // Handle initialization error
        }
        initializeOpenCVDependencies();
        //OpenCVLoader.initAsync(OpenCVLoader.OPENCV_VERSION_2_4_6, this, mLoaderCallback);
    }
}

然后是layout的xml代码：

<RelativeLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/relative"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

RelativeLayout>

现在是raw文件夹里面的xml（这个xml是图片解析出来进行对比校验人脸的模型库）由于这个文件有一千多行就不贴了，如有需要请去下载本demo查看！当然也可以去你下载的openCV的sdk里面拿，目录是\samples\face-detection\res\raw。请看图：

最后就是AndroidManifest文件了：

<manifest package="com.wyw.facedemo"
          xmlns:android="http://schemas.android.com/apk/res/android">

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

    <uses-feature android:name="android.hardware.camera" android:required="false"/>
    <uses-feature android:name="android.hardware.camera.autofocus" android:required="false"/>
    <uses-feature android:name="android.hardware.camera.front" android:required="false"/>
    <uses-feature android:name="android.hardware.camera.front.autofocus" android:required="false"/>

    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:supportsRtl="true"
        android:theme="@style/AppTheme">
        <activity android:name=".MainActivity">
            <intent-filter>
                <action android:name="android.intent.action.MAIN"/>

                <category android:name="android.intent.category.LAUNCHER"/>
            intent-filter>
        activity>
    application>

manifest>

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做到这一步就赶紧把你的代码运行起来吧！！本篇博客就到这里，如果有有疑问的欢迎留言讨论。同时希望大家多多关注我的博客，多多支持我。

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