books

assets/draw/p03/s04.dart

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+import 'dart:math';
+import 'dart:typed_data';
+import 'dart:ui';
+
+import 'package:flutter/cupertino.dart';
+import 'package:flutter/material.dart';
+import 'package:flutter/services.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 StatelessWidget {
+  const Paper({super.key});
+
+  @override
+  Widget build(BuildContext context) {
+    return Container(
+      color: Colors.white,
+      child: CustomPaint( // 使用CustomPaint
+        painter: PaperPainter(),
+      ),
+    );
+  }
+}
+
+class PaperPainter extends CustomPainter {
+  late Paint _paint;
+
+  late Paint _gridPint;
+  final double step = 20;
+  final double strokeWidth = 0.5;
+  final Color color = Colors.blue;
+
+  PaperPainter() {
+    _paint = Paint()
+      ..style = PaintingStyle.fill
+      ..strokeWidth = strokeWidth
+      ..color = color;
+    _gridPint = Paint()
+      ..style = PaintingStyle.stroke
+      ..strokeWidth = strokeWidth
+      ..color = Colors.grey;
+  }
+
+  @override
+  void paint(Canvas canvas, Size size) {
+    canvas.translate(size.width / 2, size.height / 2);
+    _drawGrid(canvas, size);
+    _drawAxis(canvas,size);
+
+    _drawPointsWithPoints(canvas);
+    // _drawPointsWithLines(canvas);
+    _drawPointLineWithPolygon(canvas);
+    _drawRawPoints(canvas);
+  }
+
+  final List<Offset> points = [
+    Offset(-120, -20),
+    Offset(-80, -80),
+    Offset(-40, -40),
+    Offset(0, -100),
+    Offset(40, -140),
+    Offset(80, -160),
+    Offset(120, -100),
+  ];
+
+  void _drawPointsWithPoints(Canvas canvas) {
+    _paint
+      ..color = Colors.red
+      ..style = PaintingStyle.stroke..strokeWidth=10
+      ..strokeCap = StrokeCap.round;
+    canvas.drawPoints(PointMode.points, points, _paint);
+  }
+
+  void _drawPointsWithLines(Canvas canvas) {
+    _paint
+      ..color = Colors.red
+      ..style = PaintingStyle.stroke
+      ..strokeWidth = 1
+      ..strokeCap = StrokeCap.round;
+    canvas.drawPoints(PointMode.lines, points, _paint);
+  }
+
+  void _drawPointLineWithPolygon(Canvas canvas) {
+    _paint
+      ..color = Colors.red
+      ..style = PaintingStyle.stroke
+      ..strokeWidth = 1
+      ..strokeCap = StrokeCap.round;
+    canvas.drawPoints(PointMode.polygon, points, _paint);
+  }
+
+  void _drawRawPoints(Canvas canvas) {
+    Float32List pos = Float32List.fromList([
+      -120, -20,-80, -80,-40,
+      -40,0, -100,40, -140,
+      80, -160,120, -100]);
+    _paint
+      ..color = Colors.red
+      ..style = PaintingStyle.stroke
+      ..strokeWidth = 10
+      ..strokeCap = StrokeCap.round;
+    canvas.drawRawPoints(PointMode.points, pos, _paint);
+  }
+
+  void _drawAxis(Canvas canvas, Size size) {
+    _paint..color=Colors.blue..strokeWidth=1.5;
+    canvas.drawLine(Offset(-size.width/2, 0) , Offset(size.width/2, 0),_paint);
+    canvas.drawLine(Offset( 0,-size.height/2) , Offset( 0,size.height/2),_paint);
+    canvas.drawLine(Offset( 0,size.height/2) , Offset( 0-7.0,size.height/2-10),_paint);
+    canvas.drawLine(Offset( 0,size.height/2) , Offset( 0+7.0,size.height/2-10),_paint);
+    canvas.drawLine(Offset(size.width/2, 0) , Offset(size.width/2-10, 7),_paint);
+    canvas.drawLine(Offset(size.width/2, 0) , Offset(size.width/2-10, -7),_paint);
+  }
+
+
+  @override
+  bool shouldRepaint(CustomPainter oldDelegate) => false;
+
+  void _drawGrid(Canvas canvas, Size size) {
+    _drawBottomRight(canvas, size);
+    canvas.save();
+    canvas.scale(1, -1); //沿x轴镜像
+    _drawBottomRight(canvas, size);
+    canvas.restore();
+
+    canvas.save();
+    canvas.scale(-1, 1); //沿y轴镜像
+    _drawBottomRight(canvas, size);
+    canvas.restore();
+
+    canvas.save();
+    canvas.scale(-1, -1); //沿原点镜像
+    _drawBottomRight(canvas, size);
+    canvas.restore();
+  }
+
+  void _drawBottomRight(Canvas canvas, Size size) {
+    canvas.save();
+    for (int i = 0; i < size.height / 2 / step; i++) {
+      canvas.drawLine(Offset(0, 0), Offset(size.width / 2, 0), _gridPint);
+      canvas.translate(0, step);
+    }
+    canvas.restore();
+
+    canvas.save();
+    for (int i = 0; i < size.width / 2 / step; i++) {
+      canvas.drawLine(Offset(0, 0), Offset(0, size.height / 2), _gridPint);
+      canvas.translate(step , 0);
+    }
+    canvas.restore();
+  }
+
+
+}