MainActivity.kt

private fun runDetector(bitmap: Bitmap) {
    val image = FirebaseVisionImage.fromBitmap(bitmap)
    val options = FirebaseVisionFaceDetectorOptions.Builder()
        .build()
    val detector = FirebaseVision.getInstance()
        .getVisionFaceDetector(options)
    detector.detectInImage(image)
        .addOnSuccessListener { faces ->
            processFaceResult(faces)
        }.addOnFailureListener {
            it.printStackTrace()
        }
}