add structure

lib/face/face_detection_image.dart

@@ -0,0 +1,59 @@
+import 'package:flutter/material.dart';
+import 'dart:io';
+import 'smile_painter.dart';
+import 'package:firebase_ml_vision/firebase_ml_vision.dart';
+import 'dart:ui' as ui show Image;
+import 'package:image_picker/image_picker.dart';
+
+class FaceDetectionFromImage extends StatefulWidget {
+  @override
+  _FaceDetectionFromImageState createState() => _FaceDetectionFromImageState();
+}
+
+class _FaceDetectionFromImageState extends State<FaceDetectionFromImage> {
+  bool loading = true;
+  ui.Image image;
+  List<Face> faces;
+  final FaceDetector faceDetector = FirebaseVision.instance.faceDetector();
+
+  Future<ui.Image> _loadImage(File file) async {
+    final data = await file.readAsBytes();
+    return await decodeImageFromList(data);
+  }
+
+  void pickAndProcessImage() async {
+    final File file = await ImagePicker.pickImage(source: ImageSource.gallery);
+    final FirebaseVisionImage visionImage = FirebaseVisionImage.fromFile(file);
+    faces = await faceDetector.processImage(visionImage);
+    image = await _loadImage(file);
+    setState(() {
+      loading = false;
+    });
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    return Scaffold(
+      appBar: AppBar(
+        title: Text('Face detection with Smile'),
+      ),
+      body: Center(
+        child: loading
+            ? Text('Press The floating Action Button for load image!')
+            : FittedBox(
+                child: SizedBox(
+                  width: image.width.toDouble(),
+                  height: image.height.toDouble(),
+                  child: FacePaint(
+                    painter: SmilePainter(image, faces),
+                  ),
+                ),
+              ),
+      ),
+      floatingActionButton: FloatingActionButton(
+        onPressed: pickAndProcessImage,
+        child: Icon(Icons.image),
+      ),
+    );
+  }
+}