1.     Android自带的人脸识别
Android自带的人脸识别只能识别出人脸在画面中的位置，中点，眼间距，角度等基本特性，提供给拍照性质的应用使用。从基本功能中不能得出明显的特征数据

2.     底层库支持
external/neven/*

3.     接口
frameworks/base/media/java/android/media/FaceDetector.java

4.     Android源码参考
packages/apps/Gallery/src/com/android/camera/*

5.     关键代码分析

package com.android.mydetect;

 

import android.app.Activity;

import android.widget.TextView;

import android.os.Bundle;

import android.media.FaceDetector;    // 人脸识别接口

import android.widget.ImageView;

import android.graphics.BitmapFactory;

import android.graphics.Bitmap;

import android.graphics.PointF;

import android.graphics.Matrix;

import android.util.Log;

import android.graphics.Canvas;

import android.graphics.Paint;

 

public class MyDetectActivity extends Activity {

       private ImageView mImageView;    // 图片显示控件

       private Bitmap mBitmap;

       private float mScale = 1F;

 

       @Override

       public void onCreate(Bundle savedInstanceState) {

                super.onCreate(savedInstanceState);

                setContentView(R.layout.main);

                mImageView = (ImageView) this.findViewById(R.id.image);

                detect();      // 识别函数

       }

 

       private void handleFace(FaceDetector.Face f) {        // 在图片上对每张脸进行处理

                PointF midPoint = new PointF();

                int r = ((int) (f.eyesDistance() * mScale * 1.5));         // 取眼睛间距离

                f.getMidPoint(midPoint);       // 取脸的中点

                midPoint.x *= mScale;

                midPoint.y *= mScale;

                Canvas c = new Canvas(mBitmap);

                Paint p = new Paint();

                p.setAntiAlias(true);

                p.setAlpha(0x80);

                c.drawCircle(midPoint.x, midPoint.y, r, p)        // 用半透明标出人脸区域;

                mImageView.setImageBitmap(mBitmap);          // 显示图片

       }

 

       private void detect() {

                Matrix matrix = new Matrix();

                FaceDetector.Face[] mFaces = new FaceDetector.Face[3];         // 定义最多识别三张脸

                int mNumFaces = 0;

 

                mBitmap = BitmapFactory.decodeResource(getResources(), R.drawable.baby);     // 取原始图

                if (mBitmap == null) {

                         return;

                }

                if (mBitmap.getWidth() > 256) {

                         mScale = 256.0F / mBitmap.getWidth();

                }

                matrix.setScale(mScale, mScale);

                Bitmap faceBitmap = Bitmap.createBitmap(mBitmap, 0, 0, mBitmap

                                   .getWidth(), mBitmap.getHeight(), matrix, true);        // 生成缩放后的新图

 

                mScale = 1.0F / mScale;

                if (faceBitmap != null) {

                         FaceDetector detector = new FaceDetector(faceBitmap.getWidth(),

                                            faceBitmap.getHeight(), mFaces.length); // 创建识别器

                         mNumFaces = detector.findFaces(faceBitmap, mFaces);    // 识别

                         if (mNumFaces > 0) {

                                   for (int i = 0; i < mNumFaces; i++) {

                                            handleFace(mFaces[i]);        // 调用函数对人脸画面进行处理

                                   }

                         }

                }

       }

}

6.     完整例程下载
http://download.csdn.net/source/2612476