Face Detection - Google ML - Android Studio - Kotlin

Detect Face using Google/Firebase ML Kit

In this tutorial, we will detect the face(s) from an image. We will use to get the Bitmap from an image in the drawable folder, but we will also show how you may also get the Bitmap from Uri, ImageView, etc.  Using the ML Kit Face Detection API, you can easily identify the key facial features & get the contours of detected faces. Note that the API only detects the faces; it doesn’t recognize the people.

With the ML Kit Face Detection API, you can easily get the information you need to perform tasks like embellishing selfies & portraits or generating avatar(s) from the user's photo. Since the ML Kit Face Detection API can perform Face Detection in real-time, you can use it in applications like video chat or games that respond to the player's expressions.

We will use the Android Studio IDE and the Kotlin language.

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Video Tutorial

Coding

build.gradle

dependencies {

    implementation 'androidx.core:core-ktx:1.7.0'
    implementation 'androidx.appcompat:appcompat:1.4.2'
    implementation 'com.google.android.material:material:1.6.1'
    implementation 'androidx.constraintlayout:constraintlayout:2.1.4'

    //Face detect library
    implementation 'com.google.mlkit:face-detection:16.1.5'

    testImplementation 'junit:junit:4.13.2'
    androidTestImplementation 'androidx.test.ext:junit:1.1.3'
    androidTestImplementation 'androidx.test.espresso:espresso-core:3.4.0'
}

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<ScrollView 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">

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:orientation="vertical">

        <!--ImageView: Original Image that will be used to detect & crop face-->
        <ImageView
            android:id="@+id/originalIv"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:adjustViewBounds="true"
            android:src="@drawable/atif01"/>

        <!--Button: Click to detect & crop face-->
        <Button
            android:id="@+id/detectFaceBtn"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:text="Detect Face"/>

        <!--ImageView: Show the detected face as cropped image-->
        <ImageView
            android:id="@+id/croppedIv"
            android:layout_width="match_parent"
            android:adjustViewBounds="true"
            android:layout_height="wrap_content"/>

    </LinearLayout>

</ScrollView>

MainActivity.kt

package com.technifysoft.myapplication

import android.graphics.Bitmap
import android.graphics.BitmapFactory
import android.os.Bundle
import android.util.Log
import android.widget.Button
import android.widget.ImageView
import android.widget.Toast
import androidx.appcompat.app.AppCompatActivity
import androidx.core.graphics.scale
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

class MainActivityy : AppCompatActivity() {

    //UI Views
    private lateinit var originalIv: ImageView
    private lateinit var croppedIv: ImageView
    private lateinit var detectFaceBtn: Button

    //Face detector
    private lateinit var detector: FaceDetector

    //constants
    private companion object{
        //This factor is used to make the detecting image smaller, to make the process faster
        private const val SCALING_FACTOR = 10
        //Tag for logging/debugging
        private const val TAG = "FACE_DETECT_TAG"
    }

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        setContentView(R.layout.activity_main)

        //init UI Views
        originalIv = findViewById(R.id.originalIv)
        croppedIv = findViewById(R.id.croppedIv)
        detectFaceBtn = findViewById(R.id.detectFaceBtn)

        // Real-time contour detection
        val realTimeFdo = FaceDetectorOptions.Builder()
            .setContourMode(FaceDetectorOptions.CONTOUR_MODE_ALL)
            .setLandmarkMode(FaceDetectorOptions.LANDMARK_MODE_ALL)
            .build()

        //init FaceDetector
        detector = FaceDetection.getClient(realTimeFdo)

        //1) Image from drawable
        val bitmap1 = BitmapFactory.decodeResource(resources, R.drawable.atifpervaiz)

        //2) Image from ImageView
        /*val bitmapDrawable = originalIv.drawable as BitmapDrawable
        val bitmap2 = bitmapDrawable.bitmap*/

        //3) Image from Uri
        /*val imageUri: Uri? = null
        try {
            val bitmap3 = MediaStore.Images.Media.getBitmap(contentResolver, imageUri)
        } catch (e: Exception) {
            Log.e(TAG, "onCreate: ", e)
        }*/

        //handle click, start detecting face
        detectFaceBtn.setOnClickListener {
            analyzePhoto(bitmap1)
        }

    }

    private fun analyzePhoto(bitmap: Bitmap){
        Log.d(TAG, "analyzePhoto: ")

        //Make image smaller to do processing faster
        val smallerBitmap = bitmap.scale(bitmap.width / SCALING_FACTOR, bitmap.height / SCALING_FACTOR, false)

        //Input Image for analyzing
        val inputImage = InputImage.fromBitmap(smallerBitmap, 0)
        //start detecting
        detector.process(inputImage)
            .addOnSuccessListener {faces->
                //Task completed
                Log.d(TAG, "analyzePhoto: Successfully detected face...")
                Toast.makeText(this, "Face Detected...", Toast.LENGTH_SHORT).show()

                for (face in faces){
                    val rect = face.boundingBox
                    rect.set(
                        rect.left * SCALING_FACTOR,
                        rect.top * (SCALING_FACTOR - 1),
                        rect.right * (SCALING_FACTOR),
                        rect.bottom * SCALING_FACTOR + 90
                    )
                }

                Log.d(TAG, "analyzePhoto: number of faces ${faces.size}")
                cropDetectedFace(bitmap, faces)
            }
            .addOnFailureListener {e->
                Log.e(TAG, "analyzePhoto: ", e)
                Toast.makeText(this, "Failed due to ${e.message}", Toast.LENGTH_SHORT).show()
            }
    }

    private fun cropDetectedFace(bitmap: Bitmap, faces: List<Face>){
        Log.d(TAG, "cropDetectedFace: ")

        //Face was detected, get cropped image as bitmap
        val rect = faces[0].boundingBox //there might be multiple images, if you want to get all use loop, im only managing 1

        val x = rect.left.coerceAtLeast(0)
        val y = rect.top.coerceAtLeast(0)

        val width = rect.width()
        val height = rect.height()

        //cropped bitmap
        val croppedBitmap = Bitmap.createBitmap(
            bitmap,
            x,
            y,
            if (x + width > bitmap.width) bitmap.width - x else width,
            if (y + height > bitmap.height) bitmap.height - y else height
        )

        //set cropped bitmap to croppedIv
        croppedIv.setImageBitmap(croppedBitmap)
    }

}

Screenshots