Display detected face area

Further works on last exercise "Face detection for Camera". Once face detected, the call-back method onFaceDetection() of FaceDetectionListener will be called with parameter of Face[], a list of face objects. The face object, Face, contain bounds of the face (rect).

A custom View, DrawingView, is added to draw rectangle to show the detected face area, over the Preview SurfaceView.

For rect, bounds of the face: (-1000, -1000) represents the top-left of the camera field of view, and (1000, 1000) represents the bottom-right of the field of view ~ Refer http://developer.android.com/reference/android/hardware/Camera.Face.html#rect.

So we have to convert from (-1000, -1000)~(1000, 1000) to (0, 0)~(width, height of the View) in onDraw() of DrawingView.

Modify the main code in AndroidCamera.java

package com.exercise.AndroidCamera;

import java.io.FileNotFoundException;
import java.io.IOException;
import java.io.OutputStream;

import android.app.Activity;
import android.content.ContentValues;
import android.content.Context;
import android.content.pm.ActivityInfo;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.PixelFormat;
import android.hardware.Camera;
import android.hardware.Camera.AutoFocusCallback;
import android.hardware.Camera.Face;
import android.hardware.Camera.FaceDetectionListener;
import android.hardware.Camera.PictureCallback;
import android.hardware.Camera.ShutterCallback;
import android.net.Uri;
import android.os.Bundle;
import android.provider.MediaStore.Images.Media;
import android.view.LayoutInflater;
import android.view.SurfaceHolder;
import android.view.SurfaceView;
import android.view.View;
import android.view.ViewGroup.LayoutParams;
import android.widget.Button;
import android.widget.LinearLayout;
import android.widget.TextView;

public class AndroidCamera extends Activity implements SurfaceHolder.Callback{

Camera camera;
SurfaceView surfaceView;
SurfaceHolder surfaceHolder;
boolean previewing = false;
LayoutInflater controlInflater = null;

Button buttonTakePicture;
TextView prompt;

DrawingView drawingView;
Face[] detectedFaces;

final int RESULT_SAVEIMAGE = 0;

/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_LANDSCAPE);

getWindow().setFormat(PixelFormat.UNKNOWN);
surfaceView = (SurfaceView)findViewById(R.id.camerapreview);
surfaceHolder = surfaceView.getHolder();
surfaceHolder.addCallback(this);
surfaceHolder.setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS);

drawingView = new DrawingView(this);
LayoutParams layoutParamsDrawing 
= new LayoutParams(LayoutParams.FILL_PARENT, 
LayoutParams.FILL_PARENT);
this.addContentView(drawingView, layoutParamsDrawing);

controlInflater = LayoutInflater.from(getBaseContext());
View viewControl = controlInflater.inflate(R.layout.control, null);
LayoutParams layoutParamsControl 
= new LayoutParams(LayoutParams.FILL_PARENT, 
LayoutParams.FILL_PARENT);
this.addContentView(viewControl, layoutParamsControl);

buttonTakePicture = (Button)findViewById(R.id.takepicture);
buttonTakePicture.setOnClickListener(new Button.OnClickListener(){

@Override
public void onClick(View arg0) {
// TODO Auto-generated method stub
camera.takePicture(myShutterCallback, 
myPictureCallback_RAW, myPictureCallback_JPG);
}});

LinearLayout layoutBackground = (LinearLayout)findViewById(R.id.background);
layoutBackground.setOnClickListener(new LinearLayout.OnClickListener(){

@Override
public void onClick(View arg0) {
// TODO Auto-generated method stub

buttonTakePicture.setEnabled(false);
camera.autoFocus(myAutoFocusCallback);
}});

prompt = (TextView)findViewById(R.id.prompt);
}

FaceDetectionListener faceDetectionListener
= new FaceDetectionListener(){

@Override
public void onFaceDetection(Face[] faces, Camera camera) {

if (faces.length == 0){
prompt.setText(" No Face Detected! ");
drawingView.setHaveFace(false);
}else{
prompt.setText(String.valueOf(faces.length) + " Face Detected :) ");
drawingView.setHaveFace(true);
detectedFaces = faces;
}

drawingView.invalidate();

}};

AutoFocusCallback myAutoFocusCallback = new AutoFocusCallback(){

@Override
public void onAutoFocus(boolean arg0, Camera arg1) {
// TODO Auto-generated method stub
buttonTakePicture.setEnabled(true);
}};

ShutterCallback myShutterCallback = new ShutterCallback(){

@Override
public void onShutter() {
// TODO Auto-generated method stub

}};

PictureCallback myPictureCallback_RAW = new PictureCallback(){

@Override
public void onPictureTaken(byte[] arg0, Camera arg1) {
// TODO Auto-generated method stub

}};

PictureCallback myPictureCallback_JPG = new PictureCallback(){

@Override
public void onPictureTaken(byte[] arg0, Camera arg1) {
// TODO Auto-generated method stub
/*Bitmap bitmapPicture 
= BitmapFactory.decodeByteArray(arg0, 0, arg0.length); */

Uri uriTarget = getContentResolver().insert(Media.EXTERNAL_CONTENT_URI, new ContentValues());

OutputStream imageFileOS;
try {
imageFileOS = getContentResolver().openOutputStream(uriTarget);
imageFileOS.write(arg0);
imageFileOS.flush();
imageFileOS.close();

prompt.setText("Image saved: " + uriTarget.toString());

} catch (FileNotFoundException e) {
// TODO Auto-generated catch block
e.printStackTrace();
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}

camera.startPreview();
camera.startFaceDetection();
}};

@Override
public void surfaceChanged(SurfaceHolder holder, int format, int width,
int height) {
// TODO Auto-generated method stub
if(previewing){
camera.stopFaceDetection();
camera.stopPreview();
previewing = false;
}

if (camera != null){
try {
camera.setPreviewDisplay(surfaceHolder);
camera.startPreview();

prompt.setText(String.valueOf(
"Max Face: " + camera.getParameters().getMaxNumDetectedFaces()));
camera.startFaceDetection();
previewing = true;
} catch (IOException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}

@Override
public void surfaceCreated(SurfaceHolder holder) {
// TODO Auto-generated method stub
camera = Camera.open();
camera.setFaceDetectionListener(faceDetectionListener);
}

@Override
public void surfaceDestroyed(SurfaceHolder holder) {
// TODO Auto-generated method stub
camera.stopFaceDetection();
camera.stopPreview();
camera.release();
camera = null;
previewing = false;
}

private class DrawingView extends View{

boolean haveFace;
Paint drawingPaint;

public DrawingView(Context context) {
super(context);
haveFace = false;
drawingPaint = new Paint();
drawingPaint.setColor(Color.GREEN);
drawingPaint.setStyle(Paint.Style.STROKE); 
drawingPaint.setStrokeWidth(2);
}

public void setHaveFace(boolean h){
haveFace = h;
}

@Override
protected void onDraw(Canvas canvas) {
// TODO Auto-generated method stub
if(haveFace){

// Camera driver coordinates range from (-1000, -1000) to (1000, 1000).
// UI coordinates range from (0, 0) to (width, height).

int vWidth = getWidth();
int vHeight = getHeight();

for(int i=0; i<detectedFaces.length; i++){

int l = detectedFaces[i].rect.left;
int t = detectedFaces[i].rect.top;
int r = detectedFaces[i].rect.right;
int b = detectedFaces[i].rect.bottom;
int left = (l+1000) * vWidth/2000;
int top  = (t+1000) * vHeight/2000;
int right = (r+1000) * vWidth/2000;
int bottom = (b+1000) * vHeight/2000;
canvas.drawRect(
left, top, right, bottom,  
drawingPaint);
}
}else{
canvas.drawColor(Color.TRANSPARENT);
}
}

}
}

Download the files.

Next: - Android 4 Face Detection: setFocusAreas() using face detected faces