本文详细介绍了Android人脸识别框架Fotoapparat的使用，从如何创建和配置FaceDetector，到FaceDetectorProcessor的工作原理，展示了如何通过FaceDetectorProcessor自定义人脸识别逻辑，并结合业务需求调用自己的算法库。
简单的集成可以参照：https://github.com/RedApparat/FaceDetector，基本的使用和介绍已经很易懂了。下面是整理的更为全面一些的学习总结。
下载github的源码之后，要到Example文件夹中去运行Demo项目，而不是-master那个层级的项目，如下图所示：
打开项目之后可以看到demo很简单，只有两个类：MainActivity和PermissionsDelegate这个运行时权限委托类，MainActivity的源码如下，由如下的代码可见，要启用人脸检测功能仅仅是调用了createFotoapparat（）这一个自定义函数：
package io.fotoapparat.facedetector.example;
import android.os.Bundle;
import android.support.annotation.NonNull;
import android.support.v7.app.AppCompatActivity;
import android.util.Log;
import android.view.View;
import java.util.List;
import io.fotoapparat.Fotoapparat;
import io.fotoapparat.FotoapparatSwitcher;
import io.fotoapparat.facedetector.Rectangle;
import io.fotoapparat.facedetector.processor.FaceDetectorProcessor;
import io.fotoapparat.facedetector.view.RectanglesView;
import io.fotoapparat.parameter.LensPosition;
import io.fotoapparat.view.CameraView;
import static io.fotoapparat.log.Loggers.fileLogger;
import static io.fotoapparat.log.Loggers.logcat;
import static io.fotoapparat.log.Loggers.loggers;
import static io.fotoapparat.parameter.selector.LensPositionSelectors.lensPosition;
public class MainActivity extends AppCompatActivity {
private final PermissionsDelegate permissionsDelegate = new PermissionsDelegate(this);
private boolean hasCameraPermission;
private CameraView cameraView;
private RectanglesView rectanglesView;
private FotoapparatSwitcher fotoapparatSwitcher;
private Fotoapparat frontFotoapparat;
private Fotoapparat backFotoapparat;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
cameraView = (CameraView) findViewById(R.id.camera_view);
rectanglesView = (RectanglesView) findViewById(R.id.rectanglesView);
hasCameraPermission = permissionsDelegate.hasCameraPermission();
if (hasCameraPermission) {
cameraView.setVisibility(View.VISIBLE);
} else {
permissionsDelegate.requestCameraPermission();
}
frontFotoapparat = createFotoapparat(LensPosition.FRONT);
backFotoapparat = createFotoapparat(LensPosition.BACK);
fotoapparatSwitcher = FotoapparatSwitcher.withDefault(backFotoapparat);
View switchCameraButton = findViewById(R.id.switchCamera);
switchCameraButton.setVisibility(
canSwitchCameras()
? View.VISIBLE
: View.GONE
);
switchCameraButton.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
switchCamera();
}
});
}
private boolean canSwitchCameras() {
return frontFotoapparat.isAvailable() == backFotoapparat.isAvailable();
}
private Fotoapparat createFotoapparat(LensPosition position) {
return Fotoapparat
.with(this)
.into(cameraView)
.lensPosition(lensPosition(position))
.frameProcessor(
FaceDetectorProcessor.with(this)
.listener(new FaceDetectorProcessor.OnFacesDetectedListener() {
@Override
public void onFacesDetected(List<Rectangle> faces) {
Log.d("&&&", "Detected faces: " + faces.size());
rectanglesView.setRectangles(faces);
}
})
.build()
)
.logger(loggers(
logcat(),
fileLogger(this)
))
.build();
}
private void switchCamera() {
if (fotoapparatSwitcher.getCurrentFotoapparat() == frontFotoapparat) {
fotoapparatSwitcher.switchTo(backFotoapparat);
} else {
fotoapparatSwitcher.switchTo(frontFotoapparat);
}
}
@Override
protected void onStart() {
super.onStart();
if (hasCameraPermission) {
fotoapparatSwitcher.start();
}
}
@Override
protected void onStop() {
super.onStop();
if (hasCameraPermission) {
fotoapparatSwitcher.stop();
}
}
@Override
public void onRequestPermissionsResult(int requestCode,
@NonNull String[] permissions,
@NonNull int[] grantResults) {
super.onRequestPermissionsResult(requestCode, permissions, grantResults);
if (permissionsDelegate.resultGranted(requestCode, permissions, grantResults)) {
fotoapparatSwitcher.start();
cameraView.setVisibility(View.VISIBLE);
}
}
}
再细看自定义函数中对于框架的具体使用，new了 Fotoapparat 这个对象，绑定了框架所引用的布局（CameraView），以及最关键最核心的人脸检测处理器（FaceDetectorProcessor）。然后去看FaceDetectorProcessor类的源码：
package io.fotoapparat.facedetector.processor;
import android.content.Context;
import android.os.Handler;
import android.os.Looper;
import java.util.List;
import io.fotoapparat.facedetector.FaceDetector;
import io.fotoapparat.facedetector.Rectangle;
import io.fotoapparat.preview.Frame;
import io.fotoapparat.preview.FrameProcessor;
/**
* {@link FrameProcessor} which detects faces on camera frames.
* <p>
* Use {@link #with(Context)} to create a new instance.
*/
public class FaceDetectorProcessor implements FrameProcessor {
private static Handler MAIN_THREAD_HANDLER = new Handler(Looper.getMainLooper());
private final FaceDetector faceDetector;
private final OnFacesDetectedListener listener;
private FaceDetectorProcessor(Builder builder) {
faceDetector = FaceDetector.create(builder.context);
listener = builder.listener;
}
public static Builder with(Context context) {
return new Builder(context);
}
@Override
public void processFrame(Frame frame) {
final List<Rectangle> faces = faceDetector.detectFaces(
frame.image,
frame.size.width,
frame.size.height,
frame.rotation
);
MAIN_THREAD_HANDLER.post(new Runnable() {
@Override
public void run() {
listener.onFacesDetected(faces);
}
});
}
/**
* Notified when faces are detected.
*/
public interface OnFacesDetectedListener {
/**
* Null-object for {@link OnFacesDetectedListener}.
*/
OnFacesDetectedListener NULL = new OnFacesDetectedListener() {
@Override
public void onFacesDetected(List<Rectangle> faces) {
// Do nothing
}
};
/**
* Called when faces are detected. Always called on the main thread.
*
* @param faces detected faces. If no faces were detected - an empty list.
*/
void onFacesDetected(List<Rectangle> faces);
}
/**
* Builder for {@link FaceDetectorProcessor}.
*/
public static class Builder {
private final Context context;
private OnFacesDetectedListener listener = OnFacesDetectedListener.NULL;
private Builder(Context context) {
this.context = context;
}
/**
* @param listener which will be notified when faces are detected.
*/
public Builder listener(OnFacesDetectedListener listener) {
this.listener = listener != null
? listener
: OnFacesDetectedListener.NULL;
return this;
}
public FaceDetectorProcessor build() {
return new FaceDetectorProcessor(this);
}
}
}
如最顶部注释所标识，FaceDetectorProcessor的作用便是可以检测手机摄像头帧上的人脸，当框架引擎检测到摄像头Frame数据后，便会进入 processFrame这个回调中，调用faceDetector.detectFaces这个方法，源码可以点进去细看，这个函数的作用便是将检测到的帧图（frame）的nv21字节数组格式（手机摄像头采集的数据格式是nv21的），大小宽高等信息作为参数传入，然后分析出识别出的人脸的关键点的信息，然后通知主线程去绘制红框，把人脸给框出来。
@Override
public void onFacesDetected(List<Rectangle> faces) {
Log.d("&&&", "Detected faces: " + faces.size());
rectanglesView.setRectangles(faces);
}
rectanglesView.setRectangles(faces)这个便是绘制函数。真正的人脸识别项目，在利用这个识别框架检测到人脸的帧图后，便会调用自己封的人脸识别so算法库了，不会用框架提供的这个faceDetector.detectFaces,毕竟关键点的信息很有限, 都会自己重写一个新的FaceDetectorProcessor，在识别之后做若干逻辑，附上部分项目中实际的覆写代码，能看到这个覆写的FaceDetectorProcessor便是在github提供的源码基础上根据业务逻辑所需改写的，调用公司自己开发的so库的格式转换和人脸关键特征点信息等等操作都尽在其中：
package com.xiaoluobei.facedetection.view.utils;
import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Rect;
import android.graphics.YuvImage;
import android.os.Environment;
import android.os.Handler;
import android.os.Looper;
import android.util.Log;
import com.xiaoluobei.facedetection.model.FaceRequesBean;
import com.xiaoluobei.facedetection.view.activity.MainActivity;
import java.io.BufferedOutputStream;
import java.io.ByteArrayOutputStream;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.nio.ByteBuffer;
import java.util.ArrayList;
import java.util.List;
import io.fotoapparat.facedetector.FaceDetector;
import io.fotoapparat.facedetector.Rectangle;
import io.fotoapparat.preview.Frame;
import io.fotoapparat.preview.FrameProcessor;
/**
* {@link FrameProcessor} which detects faces on camera frames.
* <p>
* Use {@link #with(Context)} to create a new instance.
*/
public class MTCNNFaceDetectorProcessor implements FrameProcessor {
private static Handler MAIN_THREAD_HANDLER = new Handler(Looper.getMainLooper());
private final FaceDetector faceDetector;
private final OnFacesDetectedListener listener;
private byte[] yuv = null;
private byte[] yuvr = null;
private byte[] rgb = null;
private byte[] rgba = null;
private String basePath = Environment.getExternalStorageDirectory().getPath()+ "/faceDetect/";
private static String bigBasePath = Environment.getExternalStorageDirectory().getPath()+ "/faceDetect/bigFace/";
private static String samllBasePath = Environment.getExternalStorageDirectory().getPath()+ "/faceDetect/samllFace/";
private long oldTime = 0;
private float[] faceInfoLast = null;
private MTCNNFaceDetectorProcessor(Builder builder) {
faceDetector = FaceDetector.create(builder.context);
listener = builder.listener;
}
public static Builder with(Context context) {
File file = new File(bigBasePath);
File file1 = new File(samllBasePath);
if (!file.exists()){
file.mkdirs();
}
if (!file1.exists()){
file1.mkdirs();
}
return new Builder(context);
}
@Override
public void processFrame(Frame frame) {
long newTime = System.currentTimeMillis();
long times = newTime - oldTime;
if(times < 200){
return;
}
oldTime = System.currentTimeMillis();
int width_r,height_r,rotate_r;
if(frame.rotation == 90 || frame.rotation == 270)
{
width_r = frame.size.height;
height_r = frame.size.width;
rotate_r = 360-frame.rotation;
}
else
{
width_r = frame.size.width;
height_r = frame.size.height;
rotate_r = frame.rotation;
}
long t1 = System.currentTimeMillis();
// final List<Rectangle> faces = faceDetector.detectFaces(
// frame.image,
// frame.size.width,
// frame.size.height,
// frame.rotation
// );
if(rgb == null)
{
yuv = new byte[frame.size.width * frame.size.height * 3 / 2];
yuvr = new byte[frame.size.width * frame.size.height * 3 / 2];
rgb = new byte[frame.size.width * frame.size.height * 3];
rgba = new byte[frame.size.width * frame.size.height * 4];
}
//格式转换 jni
MainActivity.vpxCoder.NV21ToI420(frame.image, yuv, frame.size.width, frame.size.height);
MainActivity.vpxCoder.YUVRotate(yuv ,yuvr, frame.size.width, frame.size.height, rotate_r);
//MainActivity.vpxCoder.YUV4202RGB(yuv, rgb, 32,frame.size.width, frame.size.height);
MainActivity.vpxCoder.YUV420ToRGB24(yuvr, rgb, 24,width_r, height_r);
long t2 = System.currentTimeMillis();
long execTime1 = t2-t1;
System.out.println("===============NV21ToRGB24:"+execTime1);
// int[] faceInfo = MainActivity.mtcnn.FaceDetect(rgb, width_r, height_r, 3);
//调用自定义so库中提供的返回人脸关键点的相关信息
float[] faceInfo = MainActivity.faceUtil.FaceDetectNew(rgb, width_r, height_r, 3,48);
long t3 = System.currentTimeMillis();
long execTime2 = t3-t2;
System.out.println("===============FaceDetect:"+execTime2);
if(faceInfo.length>1)
{
float faceNum = faceInfo[0];
final List<Rectangle> faces = new ArrayList<Rectangle>();
if(faceInfoLast == null){
faceInfoLast = faceInfo;
} else {
for(int i=0;i<faceNum;i++) {
float left, top, right, bottom, width, height;
left = faceInfo[1 + 15 * i];
top = faceInfo[2 + 15 * i];
right = faceInfo[3 + 15 * i];
bottom = faceInfo[4 + 15 * i];
width = right - left;
height = bottom - top;
Rectangle rect = new Rectangle(left/width_r,top /height_r,width/width_r,height/height_r);
faces.add(rect);
}
MAIN_THREAD_HANDLER.post(new Runnable() {
@Override
public void run() {
listener.onFacesRectangle(faces);
}
});
if (faceNum == faceInfoLast[0]) {
if (Math.abs(faceInfo[1+15*0] - faceInfoLast[1+15*0]) <= 20) {
// Log.e("过滤","过滤过滤过滤过滤过滤过滤");
faceInfoLast = faceInfo;
return;
}
}
}
faceInfoLast = faceInfo;
final FaceRequesBean faceRequesBean = new FaceRequesBean();
MainActivity.vpxCoder.YUV4202RGB(yuvr,rgba,32,width_r,height_r);
Bitmap bitmap = getPicFromBytes(rgba,width_r,height_r,faceRequesBean);
List<String> samllFaces = new ArrayList<>();
for(int i=0;i<faceNum;i++) {
float left, top, right, bottom,width , height;
// left = (float)faceInfo[1+14*i];
// top = (float)faceInfo[2+14*i];
// right = (float)faceInfo[3+14*i];
// bottom = (float)faceInfo[4+14*i];
left = faceInfo[1+15*i];
top = faceInfo[2+15*i];
right = faceInfo[3+15*i];
bottom = faceInfo[4+15*i];
width = right - left;
height = bottom - top;
// double dou = MainActivity.faceUtil.cmpImgData(rgb, width_r, height_r, 3,48);
//Rectangle rect = new Rectangle(left/width_r,top /height_r,width/width_r,height/height_r);
// getFileFromBytes(rgb, Environment.getExternalStorageDirectory().getPath()+ "/" +System.currentTimeMillis() + ".jpg");
// Bitmap nBitmap = Bitmap.createBitmap(bitmap,(int)top,(int)left,(int)height,(int)width);
Bitmap nBitmap = Bitmap.createBitmap(bitmap,(int)left,(int)top,(int)width,(int)height);
try {
String samllFace = samllBasePath + System.currentTimeMillis() + ".jpg";
FileOutputStream fout = new FileOutputStream(samllFace);
nBitmap.compress(Bitmap.CompressFormat.JPEG, 100, fout);
samllFaces.add(samllFace);
} catch (FileNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
Rectangle rect = new Rectangle(left/width_r,top /height_r,width/width_r,height/height_r);
faces.add(rect);
//画特征点
// canvas.drawPoints(new float[]{faceInfo[5+14*i],faceInfo[10+14*i],
// faceInfo[6+14*i],faceInfo[11+14*i],
// faceInfo[7+14*i],faceInfo[12+14*i],
// faceInfo[8+14*i],faceInfo[13+14*i],
// faceInfo[9+14*i],faceInfo[14+14*i]}, paint);//画多个点
}
faceRequesBean.setSmallFace(samllFaces);
// faceRequesBean.setFaces(faces);
MAIN_THREAD_HANDLER.post(new Runnable() {
@Override
public void run() {
listener.onFacesDetected(faceRequesBean);
}
});
}else{
MAIN_THREAD_HANDLER.post(new Runnable() {
@Override
public void run() {
listener.onFacesRectangle(null);
}
});
System.out.println("未检测到人脸");
}
long t4 = System.currentTimeMillis();
long execTime3 = t4-t3;
System.out.println("===============PaintTime:"+execTime3);
// if(faces.size() > 0)
// {
// System.out.println(faces.get(0).toString());
// }
}
public Bitmap getPicFromBytes(YuvImage yuvimage,int w,int h) {
ByteArrayOutputStream baos = new ByteArrayOutputStream();
yuvimage.compressToJpeg(new Rect(0, 0, w, h), 100, baos); //这里 80 是图片质量，取值范围 0-100，100为品质最高
byte[] jdata = baos.toByteArray();//这时候 bmp 就不为 null 了
Bitmap bmp = BitmapFactory.decodeByteArray(jdata, 0, jdata.length);
// Bitmap nBitmap = Bitmap.createBitmap(bitmap,(int)left,(int)top,(int)width,(int)height);
try {
FileOutputStream fout = new FileOutputStream(Environment.getExternalStorageDirectory().getPath()+ "/hh"+System.currentTimeMillis() + ".jpg");
bmp.compress(Bitmap.CompressFormat.JPEG, 100, fout);
} catch (FileNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return bmp;
}
public Bitmap getPicFromBytes(byte[] bytes,int w,int h,FaceRequesBean faceRequesBean) {
// ByteArrayOutputStream baos = new ByteArrayOutputStream();
// yuvimage.compressToJpeg(new Rect(0, 0, w, h), 80, baos); //这里 80 是图片质量，取值范围 0-100，100为品质最高
// byte[] jdata = baos.toByteArray();//这时候 bmp 就不为 null 了
// Bitmap bmp = BitmapFactory.decodeByteArray(jdata, 0, jdata.length);
//// Bitmap nBitmap = Bitmap.createBitmap(bitmap,(int)left,(int)top,(int)width,(int)height);
// try {
// FileOutputStream fout = new FileOutputStream(Environment.getExternalStorageDirectory().getPath()+ "/hh"+System.currentTimeMillis() + ".jpg");
// bmp.compress(Bitmap.CompressFormat.PNG, 100, fout);
// } catch (FileNotFoundException e) {
// // TODO Auto-generated catch block
// e.printStackTrace();
// }
// return bmp;
// BitmapFactory.Options ops = new BitmapFactory.Options();
// ops.inPreferredConfig = Bitmap.Config.ARGB_8888;
ByteBuffer bufferRGB = ByteBuffer.wrap(bytes);//将 byte 数组包装到Buffer缓冲区中
Bitmap videoBit = Bitmap.createBitmap(w, h, Bitmap.Config.ARGB_8888);//创建一个指定大小格式的Bitmap对象
videoBit.copyPixelsFromBuffer(bufferRGB);
try {
String bigFace = bigBasePath + System.currentTimeMillis() + ".jpg";
FileOutputStream fout = new FileOutputStream(bigFace);
videoBit.compress(Bitmap.CompressFormat.JPEG, 100, fout);
faceRequesBean.setBigFace(bigFace);
} catch (FileNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return videoBit;
// return BitmapFactory.decodeByteArray(bytes, 0, bytes.length,ops);
}
public static File getFileFromBytes(byte[] b, String outputFile) {
BufferedOutputStream stream = null;
File file = null;
try {
file = new File(outputFile);
FileOutputStream fstream = new FileOutputStream(file);
stream = new BufferedOutputStream(fstream);
stream.write(b);
} catch (Exception e) {
e.printStackTrace();
} finally {
if (stream != null) {
try {
stream.close();
} catch (IOException e1) {
e1.printStackTrace();
}
}
}
return file;
}
/**
* Notified when faces are detected.
*/
public interface OnFacesDetectedListener {
/**
* Null-object for {@link OnFacesDetectedListener}.
*/
OnFacesDetectedListener NULL = new OnFacesDetectedListener() {
@Override
public void onFacesDetected(FaceRequesBean faces) {
// Do nothing
}
@Override
public void onFacesRectangle(List<Rectangle> faces) {
}
};
/**
* Called when faces are detected. Always called on the main thread.
*
* @param faces detected faces. If no faces were detected - an empty list.
*/
void onFacesDetected(FaceRequesBean faces);
void onFacesRectangle(List<Rectangle> faces);
}
/**
* Builder for {@link MTCNNFaceDetectorProcessor}.
*/
public static class Builder {
private final Context context;
private OnFacesDetectedListener listener = OnFacesDetectedListener.NULL;
private Builder(Context context) {
this.context = context;
}
/**
* @param listener which will be notified when faces are detected.
*/
public Builder listener(OnFacesDetectedListener listener) {
this.listener = listener != null
? listener
: OnFacesDetectedListener.NULL;
return this;
}
public MTCNNFaceDetectorProcessor build() {
return new MTCNNFaceDetectorProcessor(this);
}
}
}
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