Voronoi Noise "highest weight out of n closest points"

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;
using System.Drawing;

namespace NoiseGeneration {
    class Program {
        static Random rnd;
        static void Main (string[] args) {

            int size = 512;
            int pointCount = 50;

            rnd = new Random(0);


            // add points
            List<Point> pointList = new List<Point>();
            while (pointList.Count < pointCount) {
                Console.Write("add point: ");
                int x = rnd.Next(size);
                int y = rnd.Next(size);
                if (pointList.Where(p => p.x == x && p.y == y).Count() == 0) {
                    pointList.Add(new Point(x, y));
                    Console.WriteLine("success");
                } else {
                    Console.WriteLine("failed");
                }
            }

            // normal voronoi
            Bitmap bitmap = new Bitmap(size, size);
            Console.Write("start processing: ");
            for (int x = 0; x < size; ++x) {
                for (int y = 0; y < size; ++y) {
                    Point current = new Point(x, y);
                    Point closest = new Point(-1, -1);
                    double dist = double.MaxValue;
                    foreach (Point p in pointList) {
                        if (Point.Distance(p, current) < dist) {
                            dist = Point.Distance(p, current);
                            closest = p;
                        }
                    }
                    bitmap.SetPixel(x, y, closest.c);
                }
            }
            Console.WriteLine("done");

            bitmap.Save("voronoi.bmp");


            // weighted voronoi
            Bitmap bitmap_w = new Bitmap(size, size);
            Console.Write("start processing: ");
            for (int x = 0; x < size; ++x) {
                for (int y = 0; y < size; ++y) {
                    Point current = new Point(x, y);

                    // sort list according to distance
                    pointList.Sort(delegate(Point a, Point b) {
                        return Math.Sign(Point.Distance(current, a) - Point.Distance(current, b));
                    });

                    List<Point> wList = pointList.GetRange(0, 3);
                    wList.Sort(delegate(Point a, Point b) {
                        return Math.Sign(b.w - a.w);
                    });

                    bitmap_w.SetPixel(x, y, wList[0].c);
                }
            }
            Console.WriteLine("done");

            bitmap_w.Save("voronoi_w.bmp");
        }
    }

    public struct Point {
        static Random rnd;
        public int x, y, w;
        public Color c;
        public Point (int _x, int _y) {
            x = _x;
            y = _y;

            if (rnd == null) {
                rnd = new Random(0);
            }
            w = rnd.Next(256);
            c = Color.FromArgb(rnd.Next(180, 320) % 256, rnd.Next(180, 320) % 256, rnd.Next(180, 320) % 256);
            //c = Color.FromArgb(w, w, w);
        }
        public static double Distance (Point a, Point b) {
            return Math.Sqrt(Math.Pow(a.x - b.x, 2) + Math.Pow(a.y - b.y, 2));
        }
    }
}