I am new to flutter trying to create image selection and rotation app. I do not know how to make an image placed inside GridTile of GridView widget rotate on predefined angle on tap event while keeping the state of the last angle rotation.

I've tried using Transform.rotate widget linked to GridTile on tap event but I am unsuccessful. I am using multi_image_picker dart plugin to select and

import 'dart:math';

import 'package:flutter/material.dart';
import 'dart:async';
import 'dart:developer' as developer;

import 'package:multi_image_picker/multi_image_picker.dart';

void main() => runApp(new MyApp());

class MyApp extends StatefulWidget {
  @override
  _MyAppState createState() => new _MyAppState();
}

class _MyAppState extends State<MyApp> {
  List<Asset> images = List<Asset>();
  String _error = 'No Error Dectected';

  @override
  void initState() {
    super.initState();
  }

  Future goToDetailsPage(BuildContext context, Asset asset) async {
    String path = await asset.filePath;
    developer.log(path, name: 'my.app.main');
    Transform.rotate(
      angle: pi/2,
      child: AssetThumb(
          asset: asset,
          width: 300,
          height: 300,
        )
    );
  }

  Widget buildGridView() {
    return GridView.count(
      crossAxisCount: 3,
      mainAxisSpacing: 3,
      children: List.generate(images.length, (index) {
        Asset asset = images[index];
        return GestureDetector(
          child: GridTile(child: AssetThumb(
          asset: asset,
          width: 300,
          height: 300,
        ),),
          onTap: () {
            goToDetailsPage(context, asset);
          },
        );
      }),
    );
  }


  Future<void> loadAssets() async {
    List<Asset> resultList = List<Asset>();
    String error = 'No Error Dectected';

    try {
      resultList = await MultiImagePicker.pickImages(
        maxImages: 300,
        enableCamera: true,
        selectedAssets: images,
        cupertinoOptions: CupertinoOptions(takePhotoIcon: "chat"),
        materialOptions: MaterialOptions(
          actionBarColor: "#abcdef",
          actionBarTitle: "Example App",
          allViewTitle: "All Photos",
          useDetailsView: false,
          selectCircleStrokeColor: "#000000",
        ),
      );

      for (var r in resultList) {
        var t = await r.filePath;
        print(t);
      }
    } on Exception catch (e) {
      error = e.toString();
    }

    // If the widget was removed from the tree while the asynchronous platform
    // message was in flight, we want to discard the reply rather than calling
    // setState to update our non-existent appearance.
    if (!mounted) return;

    setState(() {
      images = resultList;
      _error = error;
    });
  }

  @override
  Widget build(BuildContext context) {
    return new MaterialApp(
      home: new Scaffold(
        appBar: new AppBar(
          title: const Text('Plugin example app'),
        ),
        body: Column(
          children: <Widget>[
            Center(child: Text('Error: $_error')),
            RaisedButton(
              child: Text("Pick images"),
              onPressed: loadAssets,
            ),
            Expanded(
              child: buildGridView(),
            )
          ],
        ),
      ),
    );
  }
}

1. What I want is to be able to rotate images placed inside GridView tiles on predefined angle when an user taps on them and the angle state to be kept for each displayed image.
2. To be able to rotate the original source images on the phone file system and save them with new names.