Detect faces in an image using ML Kit API.

This post describes how to detect faces in images using ML KIT.

In app level build.gradle add the MK Kit dependency.

plugins {
    id 'com.android.application'
}

android {
    compileSdkVersion 30
    buildToolsVersion "30.0.3"

    defaultConfig {
        applicationId "com.example.pickfile"
        minSdkVersion 21
        targetSdkVersion 30
        versionCode 1
        versionName "1.0"

        testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
    }

    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
        }
    }
    compileOptions {
        sourceCompatibility JavaVersion.VERSION_1_8
        targetCompatibility JavaVersion.VERSION_1_8
    }
}

dependencies {
    implementation 'androidx.appcompat:appcompat:1.3.1'
    implementation 'com.google.android.material:material:1.4.0'
    implementation 'androidx.constraintlayout:constraintlayout:2.1.1'
    implementation 'com.google.android.gms:play-services-mlkit-face-detection:16.2.0'
}

In AndroidManifest.xml add metadata for MLKIT.

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.example.pickfile">
    <uses-permission android:name="android.permission.INTERNET"/>

    <application
        android:allowBackup="true"
        android:icon="@mipmap/ic_launcher"
        android:label="@string/app_name"
        android:roundIcon="@mipmap/ic_launcher_round"
        android:supportsRtl="true"
        android:usesCleartextTraffic="true"
        android:theme="@style/Theme.PickFile">
        <activity android:name=".MainActivity">
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />
                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
        <meta-data
            android:name="com.google.mlkit.vision.DEPENDENCIES"
            android:value="face" />
    </application>

</manifest>

Create your layout in activity_main.xml.

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <Button
        android:id="@+id/button1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_margin="10dp"
        android:text="PICK FILE"
        android:textSize="20sp"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent" />

    <ImageView
        android:id="@+id/imageView"
        android:layout_width="match_parent"
        android:layout_height="0dp"
        app:layout_constraintBottom_toBottomOf="parent"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toBottomOf="@+id/button1"
        tools:srcCompat="@tools:sample/avatars" />

    <TextView
        android:id="@+id/textView1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Total Faces: 0"
        android:textSize="20sp"
        app:layout_constraintBottom_toTopOf="@+id/imageView"
        app:layout_constraintEnd_toEndOf="parent"
        app:layout_constraintStart_toEndOf="@+id/button1"
        app:layout_constraintTop_toTopOf="parent" />

</androidx.constraintlayout.widget.ConstraintLayout>

In MainActivity.java use following codes.

package com.example.pickfile;

import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.Rect;
import android.net.Uri;
import android.os.Bundle;
import android.os.ParcelFileDescriptor;
import android.view.View;
import android.widget.Button;
import android.widget.ImageView;
import android.widget.TextView;

import androidx.activity.result.ActivityResultCallback;
import androidx.activity.result.ActivityResultLauncher;
import androidx.activity.result.contract.ActivityResultContracts;
import androidx.annotation.NonNull;
import androidx.appcompat.app.AppCompatActivity;

import com.google.android.gms.tasks.OnFailureListener;
import com.google.android.gms.tasks.OnSuccessListener;
import com.google.android.gms.tasks.Task;
import com.google.mlkit.vision.common.InputImage;
import com.google.mlkit.vision.face.Face;
import com.google.mlkit.vision.face.FaceDetection;
import com.google.mlkit.vision.face.FaceDetector;
import com.google.mlkit.vision.face.FaceDetectorOptions;

import java.io.FileDescriptor;
import java.io.IOException;
import java.util.List;

public class MainActivity extends AppCompatActivity {

    ImageView imageview1;
    TextView textview1;

    FaceDetectorOptions options;
    Bitmap imagebitmap;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        Button button1 = findViewById(R.id.button1);
        imageview1 = findViewById(R.id.imageView);
        textview1 = findViewById(R.id.textView1);

        button1.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                mGetContent.launch("image/*");
            }
        });

        options =
                new FaceDetectorOptions.Builder()
                        .setPerformanceMode(FaceDetectorOptions.PERFORMANCE_MODE_ACCURATE)
                        .setLandmarkMode(FaceDetectorOptions.LANDMARK_MODE_ALL)
                        .setClassificationMode(FaceDetectorOptions.CLASSIFICATION_MODE_ALL)
                        .build();

    }

    ActivityResultLauncher<String> mGetContent = registerForActivityResult(
            new ActivityResultContracts.GetContent(),
            new ActivityResultCallback<Uri>() {
                @Override
                public void onActivityResult(Uri uri) {
                    try {
                        imagebitmap = getBitmapFromUri(uri);
                        InputImage myimage = InputImage.fromFilePath(getApplicationContext(), uri);
                        processImage(myimage);
                    } catch (IOException e) {
                        e.printStackTrace();
                    }
                }
            });

    private Bitmap getBitmapFromUri(Uri uri) throws IOException {
        ParcelFileDescriptor parcelFileDescriptor =
                getContentResolver().openFileDescriptor(uri, "r");
        FileDescriptor fileDescriptor = parcelFileDescriptor.getFileDescriptor();
        Bitmap image = BitmapFactory.decodeFileDescriptor(fileDescriptor);
        parcelFileDescriptor.close();
        return image;
    }

    public void processImage(InputImage image){
        FaceDetector detector = FaceDetection.getClient(options);

        Task<List<Face>> result =
                detector.process(image)
                        .addOnSuccessListener(
                                new OnSuccessListener<List<Face>>() {
                                    @Override
                                    public void onSuccess(List<Face> faces) {
                                        // Task completed successfully
                                        displayFaces(faces);
                                    }
                                })
                        .addOnFailureListener(
                                new OnFailureListener() {
                                    @Override
                                    public void onFailure(@NonNull Exception e) {
                                        // Task failed with an exception
                                    }
                                });
    }

    public void displayFaces(List<Face> faces){
        Bitmap bitmap = Bitmap.createBitmap(imagebitmap.getWidth(), imagebitmap.getHeight(), Bitmap.Config.ARGB_8888);
        Canvas canvas = new Canvas(bitmap);
        canvas.drawBitmap(imagebitmap, 0, 0, null);

        Paint paint = new Paint(Paint.ANTI_ALIAS_FLAG);
        paint.setColor(Color.RED);
        paint.setStyle(Paint.Style.STROKE);
        paint.setStrokeWidth(3.0f);

        for (Face face : faces) {
            Rect bounds = face.getBoundingBox();
            canvas.drawRect(bounds, paint);
        }
        imageview1.setImageBitmap(bitmap);
        textview1.setText("Total faces: " + faces.size());
    }

}

Now run the app.

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