Facedetector Simple example of face recognition in Android

Android SDK from version 1.0 (API Level 1) has integrated the simple face recognition function, by calling Facedetector we can implement bitmap multi-face recognition on Android platform (can have multiple faces in a picture). It looks for the human face principle is: looks for the eye . It returns the face data of faces, by calling public float eyesdistance (), the public void Getmidpoint (PointF point), we can get the detected two-eye spacing, and the center point position of the two eyes (midpoint). Public float confidence () can return the confidence level of the face data (0~1), the greater the value, the more accurate the face data.
　

Process
1. Read a picture to bitmap (from the resource, or choose from a mobile album)
2. Using the Facedetector API to analyze the bitmap, the detected face data is stored in Facedetector.face in a list of faces;
3. Display the human face frame on the picture.

Source Code
Activity_main.xml

<linearlayout  xmlns: Android  = "http://schemas.android.com/apk/res/android"  android:layout_width  =" match_parent " android:layout_height  =" match_parent " android:orientation  =" vertical " android:padding  = "10DP" ;     <button  android:id  = "@+id/btn_select"  android:layout_width  = "match_parent"  android:layout_height  = "wrap_content"  android:text  = "select Picture" />     <button  android:id  = "@+id/btn_detect"  android:layout_width  = "match_parent"  android:layout_height  = "wrap_content"  android:layout_margintop
      = "5DP"  android:text  =" detection face "/>     <ImageViewandroid:id= "@+id/image"android:layout_width="Fill_ Parent "android:layout_height=" Fill_parent "android:layout_margintop=" 5DP " />                                </linearlayout>

Mainactivity.java

 PackageCom.example.faceandroidtest;Importandroid.app.Activity;ImportAndroid.app.ProgressDialog;ImportAndroid.content.Intent;ImportAndroid.database.Cursor;ImportAndroid.graphics.Bitmap;ImportAndroid.graphics.BitmapFactory;ImportAndroid.graphics.Canvas;ImportAndroid.graphics.Color;ImportAndroid.graphics.Paint;ImportAndroid.graphics.PointF;ImportAndroid.media.FaceDetector;ImportAndroid.media.FaceDetector.Face;ImportAndroid.net.Uri;ImportAndroid.os.AsyncTask;ImportAndroid.os.Bundle;ImportAndroid.provider.MediaStore;ImportAndroid.view.View;ImportAndroid.view.View.OnClickListener;ImportAndroid.widget.Button;ImportAndroid.widget.ImageView;ImportAndroid.widget.Toast; Public  class mainactivity extends Activity implements Onclicklistener  {    Private Static Final intRequest_code_select_pic = -;Private Static Final intMax_face_num =Ten;//maximum number of human faces to be detected    Private intRealfacenum =0;//Actual number of human faces detected    PrivateButton selectbtn;PrivateButton detectbtn;PrivateImageView image;PrivateProgressDialog PD;PrivateBitmap BM;//Bitmap object of the selected picture    PrivatePaint paint;//Paint for face area    Private Booleanhasdetected =false;//Mark whether a face is detected    @Override    protected void onCreate(Bundle savedinstancestate) {Super. OnCreate (Savedinstancestate);        Setcontentview (R.layout.activity_main);        Initview (); Paint =NewPaint ();        Paint.setcolor (Color.Blue); Paint.setstrokewidth (2); Paint.setstyle (Paint.Style.STROKE);//Set the box to be empty instead of a solid blockPD =NewProgressDialog ( This); Pd.settitle ("Hint"); Pd.setmessage ("Testing, please wait a moment"); }/** * Control initialization * /    Private void Initview() {selectbtn = (Button) Findviewbyid (r.id.btn_select); Selectbtn.setonclicklistener ( This);        DETECTBTN = (Button) Findviewbyid (r.id.btn_detect); Detectbtn.setonclicklistener ( This);    Image = (ImageView) Findviewbyid (r.id.image); }/** * Select picture from gallery */    Private void selectpicture() {Intent Intent =NewIntent ();        Intent.setaction (intent.action_get_content); Intent.settype ("image/*");    Startactivityforresult (Intent, request_code_select_pic); }@Override    protected void Onactivityresult(intRequestcode,intResultCode, Intent data) {Super. Onactivityresult (Requestcode, ResultCode, data);if(Requestcode = = Request_code_select_pic && ResultCode = = ACTIVITY.RESULT_OK) {//Get the selected pictureUri selectedimage = Data.getdata ();            String[] Filepathcolumn = {MediaStore.Images.Media.DATA}; cursor cursor = getcontentresolver (). Query (SelectedImage, Filepathcolumn,NULL,NULL,NULL); Cursor.movetofirst ();intColumnIndex = Cursor.getcolumnindex (filepathcolumn[0]);            String Selectedimagepath = cursor.getstring (columnindex); BM = Bitmapfactory.decodefile (Selectedimagepath);//To use Android built-in face recognition, the bitmap object needs to be converted to rgb_565 format, otherwise it will not be recognized .BM = Bm.copy (Bitmap.Config.RGB_565,true);            Cursor.close ();            Image.setimagebitmap (BM); hasdetected =false; }    }//private void SelectPicture () {//BM = Bitmapfactory.decoderesource (Getresources (), r.drawable.test1);//BM = Bm.copy (Bitmap.Config.RGB_565, true);//Image.setimagebitmap (BM);//hasdetected = false;//  }    /** * Detect face * *    Private void Detectface(){if(BM = =NULL) {Toast.maketext ( This,"Please select a picture first", Toast.length_short). Show ();return; }if(hasdetected) {Toast.maketext ( This,"Human face detected", Toast.length_short). Show (); }Else{NewFindfacetask (). Execute (); }    }Private void Drawfacesarea(facedetector.face[] faces) {Toast.maketext ( This,"detected in picture"+ Realfacenum +"Zhang Man's face", Toast.length_short). Show ();floatEyesdistance =0F//two eye spacingCanvas Canvas =NewCanvas (BM); for(inti =0; i < faces.length; i++) {Facedetector.face face = faces[i];if(Face! =NULL) {PointF PointF =NewPointF (); Face.getmidpoint (PointF);//Get face center pointEyesdistance = Face.eyesdistance ();//Get the distance between the eyes of the human face                //Draw the area of a human faceCanvas.drawrect (Pointf.x-eyesdistance, pointf.y-eyesdistance, pointf.x + eyesdistance, PointF.y + eyesDistance, paint)                ; hasdetected =true; }        }//Draw the face area to refresh ImageView.Image.invalidate (); }/** * Detecting the face in the image takes some time, so put it in the Asynctask to execute * @author Yubo * */    Private  class findfacetask extends asynctask<void, void, Facedetector.  Face []>{        @Override        protected void OnPreExecute() {Super. OnPreExecute ();        Pd.show (); }@Override        protectedFace[]Doinbackground(Void ... arg0) {//The key is the following three lines of codeFacedetector Facedetector =NewFacedetector (Bm.getwidth (), Bm.getheight (), max_face_num); Facedetector.face[] faces =NewFacedetector.face[max_face_num]; Realfacenum = facedetector.findfaces (BM, faces);if(Realfacenum >0){returnFaces }return NULL; }@Override        protected void OnPostExecute(face[] result) {Super. OnPostExecute (Result); Pd.dismiss ();if(Result = =NULL) {Toast.maketext (mainactivity. This,"Sorry, no face detected in the picture.", Toast.length_short). Show (); }Else{Drawfacesarea (result); }        }    } Public void OnClick(View arg0) {Switch(Arg0.getid ()) { CaseR.id.btn_select://Select PictureSelectPicture (); Break; CaseR.id.btn_detect://Detection of human faceDetectface (); Break; }    }}

In the source of the first max_face_num can be detected by the maximum number of faces set to 5.

privatestaticfinalint5;//最大可以检测出的人脸数量

Test results

The guess should be the highest recognition rate in the population of the 5 avatar, because the maximum number of faces can be detected 5, so only the highest recognition rate of the top 5 avatars.

When the maximum number of faces max_face_num can be detected is set to 10.

privatestaticfinalint10;//最大可以检测出的人脸数量

Same picture test results

Reference reference

• Android API Facial detection (face Detect)
• Using face detector in ANDROIDSDK to realize facial recognition
• face++ official website

Facedetector Simple example of face recognition in Android