Android 人脸检测实现 android人脸识别demo

Demo功能：利用android自带的人脸识别进行识别，标记出眼睛和人脸位置。点击按键后进行人脸识别，完毕后显示到imageview上。

第一部分：布局文件activity_main.xml

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/layout_main"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context=".MainActivity" >

    <TextView
        android:id="@+id/textview_hello"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@string/hello_world" />

    <ImageView
        android:id="@+id/imgview"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_below="@id/textview_hello" />

    <Button
        android:id="@+id/btn_detect_face"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_below="@id/imgview"
        android:layout_centerHorizontal="true"
        android:text="检测人脸" />

</RelativeLayout>

注意：ImageView四周的padding由布局文件里的这四句话决定:

android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"

而上面的两个margin定义在dimens.xml文件里：

<resources>

    <!-- Default screen margins, per the Android Design guidelines. -->
    <dimen name="activity_horizontal_margin">16dp</dimen>
    <dimen name="activity_vertical_margin">16dp</dimen>

</resources>

这里采用的都是默认的，可以忽略！

第二部分：MainActivity.java

package org.yanzi.testfacedetect;

import org.yanzi.util.ImageUtil;
import org.yanzi.util.MyToast;

import android.app.Activity;
import android.graphics.Bitmap;
import android.graphics.Bitmap.Config;
import android.graphics.BitmapFactory;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.Point;
import android.graphics.PointF;
import android.graphics.Rect;
import android.media.FaceDetector;
import android.media.FaceDetector.Face;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.util.DisplayMetrics;
import android.util.Log;
import android.view.Menu;
import android.view.View;
import android.view.View.OnClickListener;
import android.view.ViewGroup;
import android.view.ViewGroup.LayoutParams;
import android.widget.Button;
import android.widget.ImageView;
import android.widget.ProgressBar;
import android.widget.RelativeLayout;

public class MainActivity extends Activity {
	static final String tag = "yan";
	ImageView imgView = null;
	FaceDetector faceDetector = null;
	FaceDetector.Face[] face;
	Button detectFaceBtn = null;
	final int N_MAX = 2;
	ProgressBar progressBar = null;

	Bitmap srcImg = null;
	Bitmap srcFace = null;
	Thread checkFaceThread = new Thread(){

		@Override
		public void run() {
			// TODO Auto-generated method stub
			Bitmap faceBitmap = detectFace();
			mainHandler.sendEmptyMessage(2);
			Message m = new Message();
			m.what = 0;
			m.obj = faceBitmap;
			mainHandler.sendMessage(m);
			
		}

	};
	 Handler mainHandler = new Handler(){

		@Override
		public void handleMessage(Message msg) {
			// TODO Auto-generated method stub
			//super.handleMessage(msg);
			switch (msg.what){
			case 0:
				Bitmap b = (Bitmap) msg.obj;
				imgView.setImageBitmap(b);
				MyToast.showToast(getApplicationContext(), "检测完毕");
				break;
			case 1:
				showProcessBar();
				break;
			case 2:
				progressBar.setVisibility(View.GONE);
				detectFaceBtn.setClickable(false);
				break;
			default:
				break;
			}
		}

	};
	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.activity_main);
		initUI(); 
		initFaceDetect();
		detectFaceBtn.setOnClickListener(new OnClickListener() {

			@Override
			public void onClick(View v) {
				// TODO Auto-generated method stub
				mainHandler.sendEmptyMessage(1);
				checkFaceThread.start();
				
			}
		});



	}

	@Override
	public boolean onCreateOptionsMenu(Menu menu) {
		// Inflate the menu; this adds items to the action bar if it is present.
		getMenuInflater().inflate(R.menu.main, menu);
		return true;
	}
	public void initUI(){

		detectFaceBtn = (Button)findViewById(R.id.btn_detect_face);
		imgView = (ImageView)findViewById(R.id.imgview);
		LayoutParams params = imgView.getLayoutParams();
		DisplayMetrics dm = getResources().getDisplayMetrics();
		int w_screen = dm.widthPixels;
		//		int h = dm.heightPixels;

		srcImg = BitmapFactory.decodeResource(getResources(), R.drawable.kunlong);
		int h = srcImg.getHeight();
		int w = srcImg.getWidth();
		float r = (float)h/(float)w;
		params.width = w_screen;
		params.height = (int)(params.width * r);
		imgView.setLayoutParams(params);
		imgView.setImageBitmap(srcImg);
	}

	public void initFaceDetect(){
		this.srcFace = srcImg.copy(Config.RGB_565, true);
		int w = srcFace.getWidth();
		int h = srcFace.getHeight();
		Log.i(tag, "待检测图像: w = " + w + "h = " + h);
		faceDetector = new FaceDetector(w, h, N_MAX);
		face = new FaceDetector.Face[N_MAX];
	}
	public boolean checkFace(Rect rect){
		int w = rect.width();
		int h = rect.height();
		int s = w*h;
		Log.i(tag, "人脸 宽w = " + w + "高h = " + h + "人脸面积 s = " + s);
		if(s < 10000){
			Log.i(tag, "无效人脸，舍弃.");
			return false;
		}
		else{
			Log.i(tag, "有效人脸，保存.");
			return true;	
		}
	}
	public Bitmap detectFace(){
		//		Drawable d = getResources().getDrawable(R.drawable.face_2);
		//		Log.i(tag, "Drawable尺寸 w = " + d.getIntrinsicWidth() + "h = " + d.getIntrinsicHeight());
		//		BitmapDrawable bd = (BitmapDrawable)d;
		//		Bitmap srcFace = bd.getBitmap();

		int nFace = faceDetector.findFaces(srcFace, face);
		Log.i(tag, "检测到人脸：n = " + nFace);
		for(int i=0; i<nFace; i++){
			Face f  = face[i];
			PointF midPoint = new PointF();
			float dis = f.eyesDistance();
			f.getMidPoint(midPoint);
			int dd = (int)(dis);
			Point eyeLeft = new Point((int)(midPoint.x - dis/2), (int)midPoint.y);
			Point eyeRight = new Point((int)(midPoint.x + dis/2), (int)midPoint.y);
			Rect faceRect = new Rect((int)(midPoint.x - dd), (int)(midPoint.y - dd), (int)(midPoint.x + dd), (int)(midPoint.y + dd));
			Log.i(tag, "左眼坐标 x = " + eyeLeft.x + "y = " + eyeLeft.y);
			if(checkFace(faceRect)){
				Canvas canvas = new Canvas(srcFace);
				Paint p = new Paint();
				p.setAntiAlias(true);
				p.setStrokeWidth(8);
				p.setStyle(Paint.Style.STROKE);
				p.setColor(Color.GREEN);
				canvas.drawCircle(eyeLeft.x, eyeLeft.y, 20, p);
				canvas.drawCircle(eyeRight.x, eyeRight.y, 20, p);
				canvas.drawRect(faceRect, p);
			}

		}
		ImageUtil.saveJpeg(srcFace);
		Log.i(tag, "保存完毕");
		
		//将绘制完成后的faceBitmap返回
		return srcFace;

	}
	public void showProcessBar(){
		RelativeLayout mainLayout = (RelativeLayout)findViewById(R.id.layout_main);
		progressBar = new ProgressBar(MainActivity.this, null, android.R.attr.progressBarStyleLargeInverse); //ViewGroup.LayoutParams.WRAP_CONTENT
		RelativeLayout.LayoutParams params = new RelativeLayout.LayoutParams(ViewGroup.LayoutParams.WRAP_CONTENT, ViewGroup.LayoutParams.WRAP_CONTENT);
		params.addRule(RelativeLayout.ALIGN_PARENT_TOP, RelativeLayout.TRUE);
		params.addRule(RelativeLayout.CENTER_HORIZONTAL, RelativeLayout.TRUE);
		progressBar.setVisibility(View.VISIBLE);
		//progressBar.setLayoutParams(params);
		mainLayout.addView(progressBar, params);
		
	}


}

关于上述代码，注意以下几点：

1、在initUI()函数里初始化UI布局，主要是将ImageView的长宽比设置。根据srcImg的长宽比及屏幕的宽度，设置ImageView的宽度为屏幕宽度，然后根据比率得到ImageView的高。然后将Bitmap设置到ImageView里。一旦设置了ImageView的长和宽，Bitmap会自动缩放填充进去，所以对Bitmap就无需再缩放了。

2、initFaceDetect()函数里初始化人脸识别所需要的变量。首先将Bitmap的ARGB格式转换为RGB_565格式，这是android自带人脸识别要求的图片格式，必须进行此转化：this.srcFace = srcImg.copy(Config.RGB_565, true);

然后实例化这两个变量：

FaceDetector faceDetector = null;
FaceDetector.Face[] face;

faceDetector = new FaceDetector(w, h, N_MAX);
face = new FaceDetector.Face[N_MAX];

FaceDetector就是用来进行人脸识别的类，face是用来存放识别得到的人脸信息。N_MAX是允许的人脸个数最大值。

3、真正的人脸识别在自定义的方法detectFace()里，核心代码:faceDetector.findFaces(srcFace, face)。在识别后，通过Face f  = face[i];得到每个人脸f，通过 float dis = f.eyesDistance();得到两个人眼之间的距离，f.getMidPoint(midPoint);得到人脸中心的坐标。下面这两句话得到左右人眼的坐标：

Point eyeLeft = new Point((int)(midPoint.x - dis/2), (int)midPoint.y);
			Point eyeRight = new Point((int)(midPoint.x + dis/2), (int)midPoint.y);

下面是得到人脸的矩形：

Rect faceRect = new Rect((int)(midPoint.x - dd), (int)(midPoint.y - dd), (int)(midPoint.x + dd), (int)(midPoint.y + dd));

注意这里Rect的四个参数其实就是矩形框左上顶点的x 、y坐标和右下顶点的x、y坐标。

4、实际应用中发现，人脸识别会发生误判。所以增加函数checkFace(Rect rect)来判断，当人脸Rect的面积像素点太小时则视为无效人脸。这里阈值设为10000，实际上这个值可以通过整个图片的大小进行粗略估计到。

5、为了让用户看到正在识别的提醒，这里动态添加一个ProgressBar。代码如下：

public void showProcessBar(){
		RelativeLayout mainLayout = (RelativeLayout)findViewById(R.id.layout_main);
		progressBar = new ProgressBar(MainActivity.this, null, android.R.attr.progressBarStyleLargeInverse); //ViewGroup.LayoutParams.WRAP_CONTENT
		RelativeLayout.LayoutParams params = new RelativeLayout.LayoutParams(ViewGroup.LayoutParams.WRAP_CONTENT, ViewGroup.LayoutParams.WRAP_CONTENT);
		params.addRule(RelativeLayout.ALIGN_PARENT_TOP, RelativeLayout.TRUE);
		params.addRule(RelativeLayout.CENTER_HORIZONTAL, RelativeLayout.TRUE);
		progressBar.setVisibility(View.VISIBLE);
		//progressBar.setLayoutParams(params);
		mainLayout.addView(progressBar, params);

	}

事实上这个ProgressBar视觉效果不是太好，用ProgressDialog会更好。这里只不过是提供动态添加ProgressBar的方法。

6、程序中设置了checkFaceThread线程用来检测人脸，mainHandler用来控制UI的更新。这里重点说下Thread的构造方法，这里是模仿源码中打开Camera的方法。如果一个线程只需执行一次，则通过这种方法是最好的，比较简洁。反之，如果这个Thread在执行后需要再次执行或重新构造，不建议用这种方法，建议使用自定义Thread，程序逻辑会更容易 控制。在线程执行完毕后，设置button无法再点击，否则线程再次start便会挂掉。

Thread checkFaceThread = new Thread(){

		@Override
		public void run() {
			// TODO Auto-generated method stub
			Bitmap faceBitmap = detectFace();
			mainHandler.sendEmptyMessage(2);
			Message m = new Message();
			m.what = 0;
			m.obj = faceBitmap;
			mainHandler.sendMessage(m);

		}

	};

7、看下识别效果：

原图：

识别后：

最后特别交代下，当人眼距离少于100个像素时会识别不出来。如果静态图片尺寸较少，而手机的densityDpi又比较高的话，当图片放在drawable-hdpi文件夹下时会发生检测不到人脸的情况，同样的测试图片放在drawable-mdpi就可以正常检测。原因是不同的文件夹下，Bitmap加载进来后的尺寸大小不一样。