private fun prepareImageBase64String(): String {
        val imageStream = activity.contentResolver.openInputStream(mPictureUri)
        val selectedImage: Bitmap = BitmapFactory.decodeStream(imageStream)
        return encodeImage(selectedImage)
    }

    private fun encodeImage(bm: Bitmap): String {
        val byteArrayOutputStream = ByteArrayOutputStream()
        bm.compress(Bitmap.CompressFormat.JPEG, 40, byteArrayOutputStream)
        val bytes = byteArrayOutputStream.toByteArray()

        return Base64.encodeToString(bytes, Base64.DEFAULT)
    }