ML Kit Face Detection: Detecting Landmarks and Expressions

#android #kotlin #tutorial

Google ML Kit provides on-device face detection with landmark and expression analysis. Learn detection, feature extraction, and real-time processing.

Add ML Kit Dependency

implementation("com.google.mlkit:face-detection:16.1.5")

Basic Face Detection

import com.google.mlkit.vision.common.InputImage
import com.google.mlkit.vision.face.FaceDetection
import com.google.mlkit.vision.face.FaceDetectorOptions

val options = FaceDetectorOptions.Builder()
    .setPerformanceMode(FaceDetectorOptions.PERFORMANCE_MODE_FAST)
    .setLandmarkMode(FaceDetectorOptions.LANDMARK_MODE_ALL)
    .setClassificationMode(FaceDetectorOptions.CLASSIFICATION_MODE_ALL)
    .build()

val detector = FaceDetection.getClient(options)
val image = InputImage.fromBitmap(bitmap)

detector.process(image)
    .addOnSuccessListener { faces ->
        for (face in faces) {
            val bounds = face.boundingBox
            val rotY = face.headEulerAngleY
            val rotZ = face.headEulerAngleZ
        }
    }

Extract Face Landmarks

for (face in faces) {
    val landmarks = face.landmarks

    for (landmark in landmarks) {
        val landmarkType = landmark.landmarkType
        val position = landmark.position  // PointF(x, y)

        when (landmarkType) {
            FaceLandmark.MOUTH_BOTTOM -> { /* chin */ }
            FaceLandmark.LEFT_EYE -> { /* eye position */ }
            FaceLandmark.NOSE_BASE -> { /* nose */ }
        }
    }
}

Analyze Expressions

for (face in faces) {
    val smileProbability = face.smilingProbability ?: 0f
    val leftEyeOpenProbability = face.leftEyeOpenProbability ?: 0f
    val rightEyeOpenProbability = face.rightEyeOpenProbability ?: 0f

    when {
        smileProbability > 0.7 -> showMessage("Smiling")
        leftEyeOpenProbability < 0.3 && rightEyeOpenProbability < 0.3 ->
            showMessage("Eyes closed")
    }
}

Real-Time CameraX Integration

class FaceAnalyzer : ImageAnalysis.Analyzer {
    override fun analyze(imageProxy: ImageProxy) {
        val image = InputImage.fromMediaImage(imageProxy.image!!, imageProxy.imageInfo.rotationDegrees)
        detector.process(image)
            .addOnSuccessListener { faces ->
                updateUI(faces)
                imageProxy.close()
            }
    }
}