opencvsharp编写 RansacCircleFiler函数

以下是使用 OpenCvSharp 实现 RansacCircleFilter 函数的示例代码：

using OpenCvSharp;
using System;
using System.Collections.Generic;
using System.Linq;

public static class RansacCircleFilter
{
    public static Circle Run(List<Point2f> points, int iterations, double threshold)
    {
        if (points == null || points.Count < 3)
            throw new ArgumentException("At least 3 points are required.");

        const int minPoints = 3;

        var random = new Random();

        Circle bestCircle = null;

        for (int i = 0; i < iterations; i++)
        {
            var selectedPoints = Enumerable.Range(0, minPoints)
                .Select(_ => points[random.Next(points.Count)])
                .ToList();

            var circle = Circle.FromPoints(selectedPoints);

            if (circle == null)
                continue;

            var inliers = new List<Point2f>();
            foreach (var point in points)
            {
                var distance = Math.Abs(circle.Distance(point));
                if (distance < threshold)
                    inliers.Add(point);
            }

            if (inliers.Count > bestCircle?.Inliers?.Count)
            {
                bestCircle = new Circle(circle.Center, circle.Radius, inliers);
            }
        }

        return bestCircle;
    }
}

public class Circle
{
    public Point2f Center { get; private set; }
    public float Radius { get; private set; }
    public List<Point2f> Inliers { get; private set; }

    public Circle(Point2f center, float radius, List<Point2f> inliers)
    {
        Center = center;
        Radius = radius;
        Inliers = inliers;
    }

    public double Distance(Point2f point)
    {
        return Math.Sqrt(Math.Pow(point.X - Center.X, 2) + Math.Pow(point.Y - Center.Y, 2)) - Radius;
    }

    public static Circle FromPoints(List<Point2f> points)
    {
        if (points == null || points.Count < 3)
            return null;

        var x = points.Select(p => p.X).ToList();
        var y = points.Select(p => p.Y).ToList();
        var n = points.Count;

        var x2 = x.Select(v => v * v).ToList();
        var y2 = y.Select(v => v * v).ToList();

        var a = x.Sum();
        var b = y.Sum();

        var c = x2.Sum() + y2.Sum();

        var d = n * x2.Sum() - a * a;
        var e = n * y2.Sum() - b * b;

        var cx = (d * b - e * a) / (2 * (d * n - a * a));
        var cy = (e * a - d * b) / (2 * (e * n - b * b));

        var r = Math.Sqrt(points.Average(p => Math.Pow(p.X - cx, 2) + Math.Pow(p.Y - cy, 2)));

        return new Circle(new Point2f((float)cx, (float)cy), (float)r, points);
    }
}

这个示例中，我们使用 RANSAC 算法来拟合一个圆形，该算法可以通过迭代随机选择一些样本点，然后根据这些样本点来计算一个圆形模型，最后根据这个模型来计算圆形内的内点，并根据内点的数量选择最佳模型。