Flutter曲线拟合插件fit_curve的使用

Flutter曲线拟合插件fit_curve的使用

简介

fit_curve 是一个用于拟合曲线的插件。它实现了 Philip J. Schneider 的算法，该算法最初发表在《Graphics Gems》一书中。此实现基于 Volker Poplawski 和 Aleksandr Motsjonov 的 Python 和 JavaScript 实现。

功能

fit_curve 插件可以将一条或多条三次贝塞尔曲线拟合到多段线（polyline）。它可以处理二维和三维曲线，并且理论上也可以处理更高维度的数据。

使用示例

以下是一个简单的 Flutter 应用程序，演示如何使用 fit_curve 插件来拟合曲线。

步骤 1: 添加依赖

首先，在 pubspec.yaml 文件中添加 fit_curve 依赖：

dependencies:
  fit_curve: ^0.1.0

然后运行 flutter pub get 命令以安装依赖。

步骤 2: 创建一个简单的 Flutter 应用

创建一个新的 Flutter 项目并编辑 main.dart 文件：

import 'package:flutter/material.dart';
import 'package:fit_curve/fit_curve.dart';

void main() {
  runApp(MyApp());
}

class MyApp extends StatelessWidget {
  [@override](/user/override)
  Widget build(BuildContext context) {
    return MaterialApp(
      title: 'Flutter Fit Curve Demo',
      home: MyHomePage(),
    );
  }
}

class MyHomePage extends StatefulWidget {
  [@override](/user/override)
  _MyHomePageState createState() => _MyHomePageState();
}

class _MyHomePageState extends State<MyHomePage> {
  List<Offset> points = [
    Offset(50, 200),
    Offset(100, 100),
    Offset(200, 300),
    Offset(300, 100),
    Offset(350, 200)
  ];

  List<BezierCurve> curves = [];

  void fitCurves() {
    // 调用 fitCurve 方法来拟合曲线
    curves = fitCurve(points, error: 0.1);
  }

  [@override](/user/override)
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text('Flutter Fit Curve Demo'),
      ),
      body: Center(
        child: Column(
          mainAxisAlignment: MainAxisAlignment.center,
          children: <Widget>[
            // 显示原始点
            CustomPaint(
              size: Size(400, 400),
              painter: PointsPainter(points),
            ),
            SizedBox(height: 20),
            // 显示拟合后的曲线
            CustomPaint(
              size: Size(400, 400),
              painter: CurvesPainter(curves),
            ),
            SizedBox(height: 20),
            // 按钮触发拟合操作
            ElevatedButton(
              onPressed: () {
                fitCurves();
                setState(() {});
              },
              child: Text('Fit Curves'),
            ),
          ],
        ),
      ),
    );
  }
}

// 绘制原始点的自定义画笔
class PointsPainter extends CustomPainter {
  final List<Offset> points;

  PointsPainter(this.points);

  [@override](/user/override)
  void paint(Canvas canvas, Size size) {
    Paint paint = Paint()
      ..color = Colors.red
      ..style = PaintingStyle.stroke
      ..strokeWidth = 2;

    for (var point in points) {
      canvas.drawCircle(point, 5, paint);
    }
  }

  [@override](/user/override)
  bool shouldRepaint(CustomPainter oldDelegate) {
    return true;
  }
}

// 绘制拟合曲线的自定义画笔
class CurvesPainter extends CustomPainter {
  final List<BezierCurve> curves;

  CurvesPainter(this.curves);

  [@override](/user/override)
  void paint(Canvas canvas, Size size) {
    Paint paint = Paint()
      ..color = Colors.blue
      ..style = PaintingStyle.stroke
      ..strokeWidth = 2;

    Path path = Path();
    for (var curve in curves) {
      if (path.isEmpty) {
        path.moveTo(curve.start.x, curve.start.y);
      } else {
        path.lineTo(curve.start.x, curve.start.y);
      }
      path.cubicTo(
        curve.control1.x, curve.control1.y,
        curve.control2.x, curve.control2.y,
        curve.end.x, curve.end.y,
      );
    }
    canvas.drawPath(path, paint);
  }

  [@override](/user/override)
  bool shouldRepaint(CustomPainter oldDelegate) {
    return true;
  }
}