import 'dart:async';
import 'dart:math';

import 'package:flutter/cupertino.dart';
import 'package:flutter/material.dart';
import 'package:flutter/services.dart';
import 'dart:ui' as ui;

/// create by 张风捷特烈 on 2020-03-19
/// contact me by email 1981462002@qq.com
/// 说明: 纸

class Paper extends StatefulWidget {
  const Paper({super.key});

  @override
  _PaperState createState() => _PaperState();
}

class _PaperState extends State<Paper> {
  ui.Image? _img;
  bool get hasImage => _img != null;

  @override
  void initState() {
    _loadImage();
    super.initState();
  }
  void _loadImage() async {
    _img = await loadImageFromAssets('assets/images/wy_200x300.jpg');
    setState(() {});
  }

  //读取 assets 中的图片
  Future<ui.Image>? loadImageFromAssets(String path) async {
    ByteData data = await rootBundle.load(path);
    return decodeImageFromList(data.buffer.asUint8List());
  }

  @override
  Widget build(BuildContext context) {
    return Container(
      child: hasImage ? CustomPaint(
        painter: PaperPainter(_img) ,
      ): Container(),
    );
  }
}

class PaperPainter extends CustomPainter {
  ui.Image? img;

  PaperPainter(this.img);

  @override
  void paint(Canvas canvas, Size size) {
    if(img!=null) {
      drawImageFilter(canvas);
    }
  }

  double get imgW => img!.width.toDouble();
  double get imgH => img!.height.toDouble();



  void drawImageFilter(Canvas canvas) {
    var paint =Paint();
    _drawImage(canvas, paint,move: false);

    paint.imageFilter=ui.ImageFilter.blur(sigmaX: 0.4,sigmaY: 0.4);
    _drawImage(canvas, paint);

    paint.imageFilter=ui.ImageFilter.blur(sigmaX: 0.6,sigmaY: 0.6);
    _drawImage(canvas, paint);

    paint.imageFilter=ui.ImageFilter.blur(sigmaX: 0.8,sigmaY: 0.8);
    _drawImage(canvas, paint);

    paint.imageFilter=ui.ImageFilter.matrix(
        Matrix4.skew(pi/8,0).storage
    );
    _drawImage(canvas, paint);
  }

  void _drawImage(Canvas canvas, Paint paint,{bool move=true}) {
    if(move){
      canvas.translate(120, 0);
    }else{
      canvas.translate(20, 20);
    }
    canvas.drawImageRect(img!,
        Rect.fromLTRB(0, 0, imgW, imgH),
        Rect.fromLTRB(0, 0, imgW/2, imgH/2),
        paint);
  }

  @override
  bool shouldRepaint(CustomPainter oldDelegate) => true;
}