import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;

import android.util.Log;
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.media.FaceDetector;  //人臉識別的關鍵類
import android.media.FaceDetector.Face;
import android.view.View;

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        //setContentView(R.layout.activity_main);
        setContentView(new myView(this));   //使用自建的view來顯示
        Log.i("APP","MainActivity run here");

    }

    private class myView extends View{
        private int imageWidth, imageHeight;
        private int numberOfFace = 5;       //最大檢測的人臉數
        private FaceDetector myFaceDetect;  //人臉識別類的例項
        private FaceDetector.Face[] myFace; //儲存多張人臉的陣列變數
        float myEyesDistance;           //兩眼之間的距離
        int numberOfFaceDetected;       //實際檢測到的人臉數
        Bitmap myBitmap;

        public myView(Context context){     //view類的建構函式，必須有
            super(context);
            BitmapFactory.Options BitmapFactoryOptionsbfo = new BitmapFactory.Options();
            BitmapFactoryOptionsbfo.inPreferredConfig = Bitmap.Config.RGB_565;  //構造點陣圖生成的引數，必須為565。類名+enum
            myBitmap = BitmapFactory.decodeResource(getResources(), R.drawable.ddd, BitmapFactoryOptionsbfo);
            imageWidth = myBitmap.getWidth();
            imageHeight = myBitmap.getHeight();
            myFace = new FaceDetector.Face[numberOfFace];       //分配人臉陣列空間
            myFaceDetect = new FaceDetector(imageWidth, imageHeight, numberOfFace);
            numberOfFaceDetected = myFaceDetect.findFaces(myBitmap, myFace);    //FaceDetector 構造例項並解析人臉
            Log.i("APP","numberOfFaceDetected is " + numberOfFaceDetected);
        }

        protected void onDraw(Canvas canvas){           //override函式，必有
            canvas.drawBitmap(myBitmap, 0, 0, null);    //畫出點陣圖
            Paint myPaint = new Paint();
            myPaint.setColor(Color.GREEN);
            myPaint.setStyle(Paint.Style.STROKE);
            myPaint.setStrokeWidth(3);          //設定點陣圖上paint操作的引數

            for(int i=0; i < numberOfFaceDetected; i++){
                Face face = myFace[i];
                PointF myMidPoint = new PointF();
                face.getMidPoint(myMidPoint);
                myEyesDistance = face.eyesDistance();   //得到人臉中心點和眼間距離引數，並對每個人臉進行畫框
                canvas.drawRect(            //矩形框的位置引數
                        (int)(myMidPoint.x - myEyesDistance),
                        (int)(myMidPoint.y - myEyesDistance),
                        (int)(myMidPoint.x + myEyesDistance),
                        (int)(myMidPoint.y + myEyesDistance),
                        myPaint);
            }
        }
    }
}