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檢測人臉, 在應用中有很多用處, 可以提供更好的交互, 和一些有針對性的意見. 檢測臉部關鍵信息, 也可以更加方便的處理一些微表情的內容.

Google推出了官方的人臉檢測功能, 很不幸依賴Google Service, 需要版本8.1以上. 國內手機基本不會默認配置. 下載地址, 此版本適配手機系統4.4+.

官方API

我講解一下用法, 寫了一個簡單的顯示控件, 注釋詳細.

關注:
(1) 如何提取人臉(Face)位置.
(2) 如何提取臉部關鍵點(Landmark)位置.
(3) 如何在畫布(Canvas)居中繪制圖片.

1. 配置項目

新建HelloWorld項目, 配置build.gradle.

compile 'com.google.android.gms:play-services-vision:8.1.0' // 包含人臉識別類compile 'com.jakewharton:butterknife:7.0.1'

一般都會從最基礎的HelloWorld開始, 方便學習和理解. ButterKnife必用.

2. 檢測人臉控件

控件居中顯示一張圖片, 在圖片上, 繪制人臉位置和關鍵點(Landmarks).
關鍵點包括: 眼睛, 鼻子, 嘴等屬性. 存在遮擋, 根據不同人臉提取量不同.
通過FaceDetector檢測Bitmap, 獲取圖片的所有臉部(face)信息.
根據位置(Position)畫出臉的形狀, 根據關鍵點(Landmarks)畫出臉部特征.
同時可以獲取各種特征的概率(Probability), 和臉部偏移.

/*** 檢測人臉的控件* <p/>* Created by wangchenlong on 15/12/15.*/ public class FacesDisplayView extends View {private static final String TAG = "DEBUG-WCL: " + FacesDisplayView.class.getSimpleName();private Bitmap mBitmap; // 圖片private SparseArray<Face> mFaces; // 人臉數組// 確保圖片居中private int mHorizonOffset; // 水平偏移private int mVerticalOffset; // 豎直偏移public FacesDisplayView(Context context) {this(context, null);}public FacesDisplayView(Context context, AttributeSet attrs) {this(context, attrs, 0);}public FacesDisplayView(Context context, AttributeSet attrs, int defStyleAttr) {super(context, attrs, defStyleAttr);}// 設置顯示圖片@SuppressWarnings("unused")public void setBitmap(Bitmap bitmap) {mBitmap = bitmap;FaceDetector detector = new FaceDetector.Builder(getContext()).setTrackingEnabled(true).setLandmarkType(FaceDetector.ALL_LANDMARKS).setMode(FaceDetector.ACCURATE_MODE).build();if (!detector.isOperational()) {Log.e(TAG, "加載失敗");return;} else {Frame frame = new Frame.Builder().setBitmap(bitmap).build();mFaces = detector.detect(frame);detector.release();}logFaceData(); // 打印人臉數據invalidate(); // 填充}@Overrideprotected void onDraw(Canvas canvas) {super.onDraw(canvas);if ((mBitmap != null) && (mFaces != null)) {double scale = drawBitmap(canvas);drawFaceBox(canvas, scale);drawFaceLandmarks(canvas, scale);}}// 繪制圖片, 返回縮放概率private double drawBitmap(Canvas canvas) {double viewWidth = canvas.getWidth(); // 顯示寬度double viewHeight = canvas.getHeight(); // 顯示高度double imageWidth = mBitmap.getWidth(); // 圖片寬度double imageHeight = mBitmap.getHeight(); // 圖片高度double wScale = viewWidth / imageWidth;double hScale = viewHeight / imageHeight;double scale;Rect destBounds;// 水平豎直縮放if (wScale > hScale) {mHorizonOffset = (int) ((viewWidth - imageWidth * hScale) / 2.0f);destBounds = new Rect(mHorizonOffset, 0,(int) (imageWidth * hScale) + mHorizonOffset, (int) (imageHeight * hScale));scale = hScale;} else {mVerticalOffset = (int) ((viewHeight - imageHeight * wScale) / 2.0f);destBounds = new Rect(0, mVerticalOffset,(int) (imageWidth * wScale), (int) (imageHeight * wScale) + mVerticalOffset);scale = wScale;}canvas.drawBitmap(mBitmap, null, destBounds, null); // 添加圖片return scale;}// 繪制臉部方形private void drawFaceBox(Canvas canvas, double scale) {// 畫筆Paint paint = new Paint();paint.setColor(Color.GREEN);paint.setStyle(Paint.Style.STROKE);paint.setStrokeWidth(5);float left;float top;float right;float bottom;// 繪制每張臉for (int i = 0; i < mFaces.size(); i++) {Face face = mFaces.valueAt(i);left = (float) (face.getPosition().x * scale);top = (float) (face.getPosition().y * scale);right = (float) scale * (face.getPosition().x + face.getWidth());bottom = (float) scale * (face.getPosition().y + face.getHeight());canvas.drawRect(left + mHorizonOffset, top + mVerticalOffset,right + mHorizonOffset, bottom + mVerticalOffset, paint);}}// 繪制臉部關鍵部位private void drawFaceLandmarks(Canvas canvas, double scale) {Paint paint = new Paint();paint.setColor(Color.YELLOW);paint.setStyle(Paint.Style.STROKE);paint.setStrokeWidth(5);for (int i = 0; i < mFaces.size(); i++) {Face face = mFaces.valueAt(i);for (Landmark landmark : face.getLandmarks()) {int cx = (int) (landmark.getPosition().x * scale);int cy = (int) (landmark.getPosition().y * scale);canvas.drawCircle(cx + mHorizonOffset, cy + mVerticalOffset, 10, paint);}}}// 輸出臉部數據private void logFaceData() {float smilingProbability;float leftEyeOpenProbability;float rightEyeOpenProbability;float eulerY;float eulerZ;for (int i = 0; i < mFaces.size(); i++) {Face face = mFaces.valueAt(i);// 可能性smilingProbability = face.getIsSmilingProbability();leftEyeOpenProbability = face.getIsLeftEyeOpenProbability();rightEyeOpenProbability = face.getIsRightEyeOpenProbability();eulerY = face.getEulerY(); // 豎直軸偏移eulerZ = face.getEulerZ(); // 前后偏移Log.e(TAG, "臉數: " + i);Log.e(TAG, "微笑概率: " + smilingProbability);Log.e(TAG, "左眼睜開概率: " + leftEyeOpenProbability);Log.e(TAG, "右眼睜開概率: " + rightEyeOpenProbability);Log.e(TAG, "豎直軸偏移: " + eulerY);Log.e(TAG, "前后偏移: " + eulerZ);Log.e(TAG, "--------------------");}} }

圖像和特征是顯示在畫布上, 根據畫布大小, 等比例縮放, 并居中顯示.

3. 主頁面

主界面通過一個簡單的ViewPager連續顯示圖片.

@Bind(R.id.main_vp_container) ViewPager mVpContainer; // 連續@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);ButterKnife.bind(this);Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);setSupportActionBar(toolbar);mVpContainer.setAdapter(new FacesViewPagerAdapter(getSupportFragmentManager()));}

適配傳遞參數, 根據參數, 返回不同的圖片頁面.

/*** 臉部適配器* <p/>* Created by wangchenlong on 15/12/15.*/ public class FacesViewPagerAdapter extends FragmentPagerAdapter {private static final int NUM = 9;public FacesViewPagerAdapter(FragmentManager fm) {super(fm);}@Override public Fragment getItem(int position) {return ShowFaceFragment.newInstance(position);}@Override public int getCount() {return NUM;} }

每頁是個Fragment, 根據參數, 使用不同資源.

/*** 顯示人臉的界面* <p/>* Created by wangchenlong on 15/12/15.*/ public class ShowFaceFragment extends Fragment {private static final String ARG_SELECTION_NUM = "arg_selection_num";@Bind(R.id.main_fdv_face_detector) FacesDisplayView mFdvFaceDetector;@RawRes ArrayList<Integer> mPhotos; // 圖片集合public ShowFaceFragment() {mPhotos = new ArrayList<>();mPhotos.add(R.raw.total_large_poster);mPhotos.add(R.raw.jessicajung_large_poster);mPhotos.add(R.raw.seohyun_large_poster);mPhotos.add(R.raw.sooyoung_large_poster);mPhotos.add(R.raw.sunny_large_poster);mPhotos.add(R.raw.taeyeon_large_poster);mPhotos.add(R.raw.tiffany_large_poster);mPhotos.add(R.raw.yoona_large_poster);mPhotos.add(R.raw.yuri_large_poster);}public static ShowFaceFragment newInstance(int selectionNum) {ShowFaceFragment simpleFragment = new ShowFaceFragment();Bundle args = new Bundle();args.putInt(ARG_SELECTION_NUM, selectionNum);simpleFragment.setArguments(args);return simpleFragment;}@Nullable @Overridepublic View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {View view = inflater.inflate(R.layout.fragment_show_face, container, false);ButterKnife.bind(this, view);return view;}@Override public void onViewCreated(View view, @Nullable Bundle savedInstanceState) {super.onViewCreated(view, savedInstanceState);@RawRes int image = mPhotos.get(getArguments().getInt(ARG_SELECTION_NUM));InputStream stream = getResources().openRawResource(image);Bitmap bitmap = BitmapFactory.decodeStream(stream);mFdvFaceDetector.setBitmap(bitmap);}@Override public void onDestroyView() {super.onDestroyView();ButterKnife.unbind(this);} }

注意使用注釋(Annotation), 判斷資源類型, 如@RawRes.

Github下載地址

有時間再完善一下這個小控件吧.

OK, Enjoy It.

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