Android实现人脸识别的详细过程

来源：互联网发布：日本留学生中国知乎编辑：程序博客网时间：2024/06/05 17:27

照相时，在预览画面上提示用户人脸的位置，并完成自动对焦等，是个错的应用; 下面是实现细节，我们知道在android的代码中已有人脸识别的底层算法代码，而且在framework层也封了调用的API函数

extern/neven 目录下是实现人脸识别的算法代码。
添加获取照相时预览图片数据，可以在onPreviewFrame回调函数中得。在开始预览的地方，用
mCameraDevice.setPreviewCallback(mPreviewCallback);设置预览回调函数。

import android.media.FaceDetector;
import android.media.FaceDetector.Face;
//Harrison add
private void DrawRectOnFace() {
if (numberOfFaceDetected != 0) {
Face mFace1 = mFace[0];
PointF midPoint = new PointF();
mFace1.getMidPoint(midPoint);
if ((Math.abs(mPreMidPoint.x-midPoint.x) < 50) && (Math.abs(mPreMidPoint.y-midPoint.y) < 50)) {
Log.i("Harrison", "not draw Rect .");
return ;
}
mPreMidPoint.x = midPoint.x;
mPreMidPoint.y = midPoint.y;
mFindFaceView.setVisibility(View.VISIBLE);
} else {
mPreMidPoint.x = 0;
mPreMidPoint.y = 0;
mFindFaceView.clearDraw();
mFindFaceView.setVisibility(View.GONE);
return;
}
mFindFaceView.drawRects(mFace, numberOfFaceDetected);
}
//调用API找人脸，需要import进软件包哦！
private void FindFacesInBitmap(Bitmap myBitmap) {
imageWidth = myBitmap.getWidth();
imageHeight = myBitmap.getHeight();
Log.i("Harrison", "imageWidth="+imageWidth+", imageHeight="+imageHeight);
mFace = new FaceDetector.Face[numberOfFace];
mFaceDetect = new FaceDetector(imageWidth, imageHeight, numberOfFace);
numberOfFaceDetected = mFaceDetect.findFaces(myBitmap, mFace);
Log.i("Harrison", "numberOfFaceDetected="+numberOfFaceDetected);
}
private Bitmap rotateMyBitmap(Bitmap bitmap) {
int width = bitmap.getWidth();
int height = bitmap.getHeight();
Matrix matrix = new Matrix();
matrix.postRotate(90);
Bitmap rotateBitmap = Bitmap.createBitmap(bitmap, 0, 0, width, height, matrix, true);
return rotateBitmap;
}
private Bitmap scaleMyBitmap(Bitmap bitmap) {
int width = bitmap.getWidth();
int height = bitmap.getHeight();
int nWidth = mFindFaceView.getFaceViewWidth();;
int nHeight = mFindFaceView.getFaceViewHeight();
// Log.i("Harrison", "nWidth="+nWidth+", nHeight"+nHeight);
float scaleWidth = ((float) nWidth)/width;
float scaleHeight = ((float)nHeight)/height;
Matrix matrix = new Matrix();
matrix.postScale(scaleWidth, scaleHeight);
Bitmap resizedBitmap = Bitmap.createBitmap(bitmap, 0, 0, width, height, matrix, true);
return resizedBitmap;
}
//处理图片格式，一般摄像头抓到的数据为ImageFormat.NV21，不同的格式，需要调整的。
private void decodeToBitMap(byte[] data, android.hardware.Camera _camera) {
mCameraDevice.setPreviewCallback(null);
Size size = mCameraDevice.getParameters().getPreviewSize();
//FileOutputStream outStream = null;
try {
YuvImage image = new YuvImage(data, ImageFormat.NV21, size.width, size.height, null);
if (image != null) {
ByteArrayOutputStream stream = new ByteArrayOutputStream();
image.compressToJpeg(new Rect(0, 0, size.width, size.height), 80, stream);
// outStream = new FileOutputStream(String.format("/sdcard/%d.jpg", System.currentTimeMillis()));
// outStream.write(stream.toByteArray());
// outStream.close();
// Log.i("Harrison", "write file to sdcard.");
//在我的手机上有两种预览模式，发现全屏模式时需要调整图片的大小才能正确定位。
Bitmap myBitmap=BitmapFactory.decodeByteArray(stream.toByteArray(), 0, stream.size());
stream.close();
if (mPreviewLayoutProxy.getFullScreenMode()) { // fullscreen mode
Bitmap tmpScaleBmp=null;
Bitmap tmpRotateBmp=null;
//手机是竖屏横排是与其别的哦
if (((mOrientation/90) == 0) || ((mOrientation/90) == 2)) {
tmpRotateBmp = rotateMyBitmap(myBitmap);
tmpScaleBmp = scaleMyBitmap(tmpRotateBmp);
FindFacesInBitmap(tmpScaleBmp);
if (tmpRotateBmp != null) {
tmpRotateBmp.recycle();
tmpRotateBmp = null;
}
} else {
FindFacesInBitmap(scaleMyBitmap(myBitmap));
}
if (tmpScaleBmp != null) {
tmpScaleBmp.recycle();
tmpScaleBmp = null;
}
} else { //normal mode
FindFacesInBitmap(myBitmap);
}
DrawRectOnFace();
if (myBitmap != null) {
myBitmap.recycle();
myBitmap = null;
}
}
} catch (Exception ex) {
Log.e("Sys", "Error:" + ex.getMessage());
}
mCameraDevice.setPreviewCallback(mPreviewCallback);
}
private final class PostPreviewCallback implements PreviewCallback {
@Override
public void onPreviewFrame(byte[] data, android.hardware.Camera camera) {
decodeToBitMap(data, camera);
}
}

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我们知道，相机预览是用 SurfaceView来显示图片的；在我们画提示框时，不能直接用那个view的，会出现黑屏的状态，预览的画面也不流畅的。添加一个一样大小的SurfaceView来提示。
在xml布局中添加

<SurfaceView android:id="@+id/camera_preview"
android:layout_width="match_parent"
android:layout_height="match_parent"/>
<com.android.camera.FindFaceView
android:id="@+id/faces_rectangle"
android:layout_width="fill_parent"
android:layout_height="fill_parent" />

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我的画提示框代码：

package com.android.camera;
import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Bitmap;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.Rect;
import android.graphics.Paint.Style;
import android.graphics.PixelFormat;
import android.graphics.PorterDuffXfermode;
import android.graphics.PorterDuff;
import android.util.AttributeSet;
import android.util.Log;
import android.view.SurfaceHolder;
import android.view.SurfaceView;
import android.view.View;
import android.graphics.PointF;
import android.media.FaceDetector;
import android.media.FaceDetector.Face;
public class FindFaceView extends SurfaceView implements SurfaceHolder.Callback{
protected SurfaceHolder sh;
private SurfaceHolder mCameraSh;
private int mWidth;
private int mHeight;
private float mEyesDistance;
public FindFaceView(Context context, AttributeSet attrs) {
super(context, attrs);
// TODO Auto-generated constructor stub
sh = getHolder();
sh.addCallback(this);
sh.setFormat(PixelFormat.TRANSPARENT);
setZOrderOnTop(true);
}
public void surfaceChanged(SurfaceHolder arg0, int arg1, int w, int h) {
// TODO Auto-generated method stub
mWidth = w;
mHeight = h;
}
public void surfaceCreated(SurfaceHolder arg0) {
// TODO Auto-generated method stub
}
public void surfaceDestroyed(SurfaceHolder arg0) {
// TODO Auto-generated method stub
}
void setCameraPreviewSurfaceHolder(SurfaceHolder sh) {
mCameraSh = sh;
}
public int getFaceViewWidth() {
return mWidth;
}
public int getFaceViewHeight() {
return mHeight;
}
void clearDraw() {
Canvas canvas = sh.lockCanvas();
Paint clipPaint = new Paint();
clipPaint.setAntiAlias(true);
clipPaint.setStyle(Paint.Style.STROKE);
clipPaint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.CLEAR));
canvas.drawPaint(clipPaint);
sh.unlockCanvasAndPost(canvas);
}
public void drawRects(FaceDetector.Face[] mFace, int numberOfFaceDetected) {
Canvas canvas = sh.lockCanvas();
Paint clipPaint = new Paint();
clipPaint.setAntiAlias(true);
clipPaint.setStyle(Paint.Style.STROKE);
clipPaint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.CLEAR));
canvas.drawPaint(clipPaint);
canvas.drawColor(Color.TRANSPARENT);
Paint p = new Paint();
p.setAntiAlias(true);
p.setColor(Color.RED);
p.setStyle(Style.STROKE);
for (int i = 0; i < numberOfFaceDetected; i++) {
// if (0 == i) {
// p.setColor(Color.WHITE);
// } else {
// p.setColor(Color.GRAY);
// }
Face face = mFace[i];
PointF myMidPoint = new PointF();
face.getMidPoint(myMidPoint);
mEyesDistance = face.eyesDistance();
Log.i("Harrison", "i="+i+"("+myMidPoint.x+", "+myMidPoint.y+")");
canvas.drawRect((int)(myMidPoint.x-mEyesDistance),
(int)(myMidPoint.y-mEyesDistance),
(int)(myMidPoint.x+mEyesDistance),
(int)(myMidPoint.y+mEyesDistance),
p);
}
sh.unlockCanvasAndPost(canvas);
}
//测试两个View是否错移
public void drawBitmap(Bitmap myBitmap) {
Canvas canvas = sh.lockCanvas();
canvas.drawBitmap(myBitmap, 0, 0, null);
sh.unlockCanvasAndPost(canvas);
// mImage.setImageBitmap(myBitmap);
// mImage.invalidate();
}
public void doDraw() {
Canvas canvas = sh.lockCanvas();
canvas.drawColor(Color.TRANSPARENT);// 这里是绘制背景
Paint p = new Paint(); // 笔触
p.setAntiAlias(true); // 反锯齿
p.setColor(Color.RED);
p.setStyle(Style.STROKE);
canvas.drawLine(mWidth/2 - 100, 0, mWidth/2 - 100, mHeight, p);
canvas.drawLine(mWidth/2 + 100, 0, mWidth/2 + 100, mHeight, p);
// ------------------------
// 画边框---------------------
Rect rec = canvas.getClipBounds();
rec.bottom--;
rec.right--;
p.setColor(Color.GRAY);
// 颜色
p.setStrokeWidth(5);
canvas.drawRect(rec, p);
// 提交绘制
sh.unlockCanvasAndPost(canvas);
}
}

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