books

assets/draw/p04/s01.dart

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+import 'dart:async';
+import 'dart:ui' as ui;
+
+import 'package:flutter/cupertino.dart';
+import 'package:flutter/material.dart';
+import 'package:flutter/services.dart';
+
+import '../components/coordinate.dart';
+
+
+
+/// 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? _image;
+
+  @override
+  void initState() {
+    super.initState();
+    _loadImage();
+  }
+
+  void _loadImage() async {
+    _image =
+    await loadImageFromAssets('assets/images/wy_300x200.jpg');
+    setState(() {});
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    return Container(
+        color: Colors.white, child: CustomPaint(painter: PaperPainter(_image)));
+  }
+
+  //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());
+  }
+}
+
+class PaperPainter extends CustomPainter {
+  late Paint _paint;
+
+  final double strokeWidth = 0.5;
+  final Color color = Colors.blue;
+
+  final ui.Image? image;
+  final Coordinate coordinate = Coordinate();
+
+  PaperPainter(this.image) {
+    _paint = Paint()
+      ..style = PaintingStyle.fill
+      ..strokeWidth = strokeWidth
+      ..color = color;
+  }
+
+  @override
+  void paint(Canvas canvas, Size size) {
+    coordinate.paint(canvas, size);
+    canvas.translate(size.width / 2, size.height / 2);
+    _drawImage(canvas);
+  }
+
+  @override
+  bool shouldRepaint(PaperPainter oldDelegate) =>
+      image != oldDelegate.image;
+
+  void _drawImage(Canvas canvas) {
+    if (image != null) {
+      canvas.drawImage(
+          image!, Offset(-image!.width / 2, -image!.height / 2), _paint);
+    }
+  }
+}