import 'dart:async';

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) {
      drawColorFilter(canvas);
    }
  }

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

  void drawColorFilter(Canvas canvas) {
    var paint =Paint();
    const ColorFilter identity = ColorFilter.matrix(<double>[
      1, 0, 0, 0, 0,
      0, 1, 0, 0, 0,
      0, 0, 1, 0, 0,
      0, 0, 0, 1, 0,
    ]);
    _drawImage(canvas, paint..colorFilter=identity,move: false);

    const ColorFilter sepia = ColorFilter.matrix(<double>[
      0.393, 0.769, 0.189, 0, 0,
      0.349, 0.686, 0.168, 0, 0,
      0.272, 0.534, 0.131, 0 , 0,
      0,     0,     0,     1, 0,
    ]);
    _drawImage(canvas, paint..colorFilter=sepia);

    const ColorFilter invert = ColorFilter.matrix(<double>[
      -1,  0,  0, 0, 255,
      0, -1,  0, 0, 255,
      0,  0, -1, 0, 255,
      0,  0,  0, 1,   0,
    ]);
    _drawImage(canvas, paint..colorFilter=invert);

    const ColorFilter greyscale = ColorFilter.matrix(<double>[
      0.2126, 0.7152, 0.0722, 0, 0,
      0.2126, 0.7152, 0.0722, 0, 0,
      0.2126, 0.7152, 0.0722, 0, 0,
      0,      0,      0,      1, 0,
    ]);
    _drawImage(canvas, paint..colorFilter=greyscale);

    const n = 90.0;
    const ColorFilter light = ColorFilter.matrix(<double>[
      1,0,0,0,n,
      0,1,0,0,n,
      0,0,1,0,n,
      0,0,0,1,0
    ]);
    _drawImage(canvas, paint..colorFilter=light);
  }

  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;
}