image rotate and scale

imageScaleAndRotate.dart

import 'dart:async';
import 'dart:math';
import 'dart:typed_data';
import 'dart:ui' as ui;
import 'package:flutter/services.dart' show rootBundle;
import 'package:flutter/material.dart' hide Image;

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


ThemeData theme =  new ThemeData(
    primaryColor: Colors.black,
    backgroundColor: Colors.white10
);

class MyApp extends StatelessWidget {
  // This widget is the root of your application.
  @override
  Widget build(BuildContext context) {
    return new MaterialApp(
      title: 'Photo View example',
      theme: theme,
      home: new Scaffold(
        body: new Home(),
      ),
    );
  }
}


class Home extends StatelessWidget{

  Future<ui.Image> loadImage() async {
    ByteData data = await rootBundle.load("graphics/test.jpg");
    if (data == null) {
      print("data is null");
    } else {
      var codec = await ui.instantiateImageCodec(data.buffer.asUint8List());
      var frame = await codec.getNextFrame();
      return frame.image;
    }
  }

  @override
        Widget build(BuildContext context) {
          return Container(
            constraints: BoxConstraints.expand(), 
            child: FutureBuilder(
              future: loadImage(),
              builder: (BuildContext context, AsyncSnapshot<ui.Image> snapshot) {
                switch(snapshot.connectionState) {
                  case ConnectionState.waiting : 
                    return Center(child: Text("loading..."),);
                  default:
                    if (snapshot.hasError) {
                      return Center(child: Text("error: ${snapshot.error}"),);
                    } else {
                      return ImagePainter(image: snapshot.data);
                    }
                  }
                },
              ),
          );
        }
}


class ImagePainter extends StatefulWidget {

  ui.Image image;

  ImagePainter({this.image}) : assert(image != null);
  @override
  State<StatefulWidget> createState() {
    return ImagePainterState();
  }
}


class ImagePainterState extends State<ImagePainter> {


  @override
  Widget build(BuildContext context) {
    return CustomPaint(
      painter: CustomImagePainter(image: widget.image),
    );
  }
}

class CustomImagePainter extends CustomPainter {

  ui.Image image;

  CustomImagePainter({this.image}): assert(image != null);

  @override
  void paint(ui.Canvas canvas, ui.Size size) {
    // TODO: implement paint
    Offset imageSize = Offset(image.width.toDouble(), image.height.toDouble());
    Paint paint = new Paint()
                  ..color = Colors.green;
    // canvas.drawCircle(size.center(Offset.zero), 20.0, paint);

    print(size);
    canvas.save();
    var scale = size.width / image.width;
    canvas.scale(scale);
    // canvas.translate(image.width/2 * scale, image.height/2 * scale);
    // canvas.rotate(45 * PI /180);
    // canvas.translate(- image.width /2/ scale, - image.height/2/scale);
    canvas.drawImage(image, Offset.zero, paint);
    

  }

  @override
  bool shouldRepaint(CustomPainter oldDelegate) {
    return false;
  }

}