Face detection is a cool and fun hidden api feature of Android, and has been around since Android 1.5. In essence face detection is part of a machine learning technique of recognizing objects using a set of features. Its cool to identify those party buddies and handy to those you want to avoid….hahah!

Some example results of Android’s face detection capabilites:

Ok..sometimes its handy to identify those beer bottles as well….mmh

Faces and Beer Bottles identified

With Image annotation:

Download: http://www.filefactory.com/file/cbf2e8b/n/AndroFaces-Example.zip

File: Main.java

import android.app.Activity;
import android.os.Bundle;

public class Main extends Activity
{
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(new FaceDetectionView(this, "face5.JPG"));
}
}


<strong>File: FaceDetectionView.java</strong>


import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.PointF;
import android.graphics.Rect;
import android.media.FaceDetector;
import android.util.Log;
import android.view.View;

/**
* @author wdavid01
*
*/
public class FaceDetectionView extends View
{
private static final String tag = FaceDetectionView.class.getName();
private static final int NUM_FACES = 10;
private FaceDetector arrayFaces;
private final FaceDetector.Face getAllFaces[] = new FaceDetector.Face[NUM_FACES];
private FaceDetector.Face getFace = null;

private final PointF eyesMidPts[] = new PointF[NUM_FACES];
private final float eyesDistance[] = new float[NUM_FACES];

private Bitmap sourceImage;

private final Paint tmpPaint = new Paint(Paint.ANTI_ALIAS_FLAG);
private final Paint pOuterBullsEye = new Paint(Paint.ANTI_ALIAS_FLAG);
private final Paint pInnerBullsEye = new Paint(Paint.ANTI_ALIAS_FLAG);

private int picWidth, picHeight;
private float xRatio, yRatio;
private ImageLoader mImageLoader = null;

public FaceDetectionView(Context context, String imagePath)
{
super(context);
init();
mImageLoader = ImageLoader.getInstance(context);
sourceImage = mImageLoader.loadFromFile(imagePath);
detectFaces();

}

private void init()
{
Log.d(tag, "Init()...");
pInnerBullsEye.setStyle(Paint.Style.FILL);
pInnerBullsEye.setColor(Color.RED);
pOuterBullsEye.setStyle(Paint.Style.STROKE);
pOuterBullsEye.setColor(Color.RED);
tmpPaint.setStyle(Paint.Style.STROKE);
tmpPaint.setTextAlign(Paint.Align.CENTER);
BitmapFactory.Options bfo = new BitmapFactory.Options();
bfo.inPreferredConfig = Bitmap.Config.RGB_565;

}

private void loadImage(String imagePath)
{
sourceImage = mImageLoader.loadFromFile(imagePath);
}

@Override
protected void onDraw(Canvas canvas)
{
Log.d(tag, "onDraw()...");

xRatio = getWidth() * 1.0f / picWidth;
yRatio = getHeight() * 1.0f / picHeight;
canvas.drawBitmap(sourceImage, null, new Rect(0, 0, getWidth(), getHeight()), tmpPaint);
for (int i = 0; i &lt; eyesMidPts.length; i++)
{
if (eyesMidPts[i] != null)
{
pOuterBullsEye.setStrokeWidth(eyesDistance[i] / 6);
canvas.drawCircle(eyesMidPts[i].x * xRatio, eyesMidPts[i].y * yRatio, eyesDistance[i] / 2, pOuterBullsEye);
canvas.drawCircle(eyesMidPts[i].x * xRatio, eyesMidPts[i].y * yRatio, eyesDistance[i] / 6, pInnerBullsEye);
}
}
}

private void detectFaces()
{
Log.d(tag, "detectFaces()...");

picWidth = sourceImage.getWidth();
picHeight = sourceImage.getHeight();

arrayFaces = new FaceDetector(picWidth, picHeight, NUM_FACES);
arrayFaces.findFaces(sourceImage, getAllFaces);

for (int i = 0; i &lt; getAllFaces.length; i++)
{
getFace = getAllFaces[i];
try
{
PointF eyesMP = new PointF();
getFace.getMidPoint(eyesMP);
eyesDistance[i] = getFace.eyesDistance();
eyesMidPts[i] = eyesMP;

Log.i("Face", i + " " + getFace.confidence() + " " + getFace.eyesDistance() + " " + "Pose: (" + getFace.pose(FaceDetector.Face.EULER_X) + "," + getFace.pose(FaceDetector.Face.EULER_Y) + "," + getFace.pose(FaceDetector.Face.EULER_Z) + ")" + "Eyes Midpoint: (" + eyesMidPts[i].x + "," + eyesMidPts[i].y + ")");

}
catch (Exception e)
{
Log.e("Face", i + " is null");
}
}
}
}
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