add structure

lib/face/utils.dart

@@ -0,0 +1,69 @@
+import 'dart:async';
+import 'dart:typed_data';
+import 'dart:ui';
+import 'package:camera/camera.dart';
+import 'package:firebase_ml_vision/firebase_ml_vision.dart';
+import 'package:flutter/foundation.dart';
+
+typedef HandleDetection = Future<List<Face>> Function(FirebaseVisionImage image);
+
+Future<CameraDescription> getCamera(CameraLensDirection dir) async {
+  return await availableCameras().then(
+        (List<CameraDescription> cameras) => cameras.firstWhere(
+          (CameraDescription camera) => camera.lensDirection == dir,
+    ),
+  );
+}
+
+Uint8List concatenatePlanes(List<Plane> planes) {
+  final WriteBuffer allBytes = WriteBuffer();
+  planes.forEach((Plane plane) => allBytes.putUint8List(plane.bytes));
+  return allBytes.done().buffer.asUint8List();
+}
+
+FirebaseVisionImageMetadata buildMetaData(
+    CameraImage image,
+    ImageRotation rotation,
+    ) {
+  return FirebaseVisionImageMetadata(
+    rawFormat: image.format.raw,
+    size: Size(image.width.toDouble(), image.height.toDouble()),
+    rotation: rotation,
+    planeData: image.planes.map(
+          (Plane plane) {
+        return FirebaseVisionImagePlaneMetadata(
+          bytesPerRow: plane.bytesPerRow,
+          height: plane.height,
+          width: plane.width,
+        );
+      },
+    ).toList(),
+  );
+}
+
+Future<List<Face>> detect(
+    CameraImage image,
+    HandleDetection handleDetection,
+    ImageRotation rotation,
+    ) async {
+  return handleDetection(
+    FirebaseVisionImage.fromBytes(
+      concatenatePlanes(image.planes),
+      buildMetaData(image, rotation),
+    ),
+  );
+}
+
+ImageRotation rotationIntToImageRotation(int rotation) {
+  switch (rotation) {
+    case 0:
+      return ImageRotation.rotation0;
+    case 90:
+      return ImageRotation.rotation90;
+    case 180:
+      return ImageRotation.rotation180;
+    default:
+      assert(rotation == 270);
+      return ImageRotation.rotation270;
+  }
+}