OpenCvSharp でお絵かき。なめらかな曲線を描ける。

MouseClickPolylinesCanvasWindow.cs

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

namespace OpenCvSharpSample.Samples
{
    public class MethodTest
    {
        public static void MouseClickPolylinesCanvasWindow()
        {
            using (var window = new Window("canvas"))
            {
                var pointList = new List<List<Point>>();
                bool moving = false;

                var color = new Scalar(100, 100, 0);
                var mat = new Mat(new Size(640, 480), MatType.CV_8UC3);
                mat.SetTo(new Scalar(255, 255, 255));

                window.ShowImage(mat);
                window.OnMouseCallback += (e, x, y, flags) =>
                {
                    if (e == MouseEvent.LButtonDown)
                    {
                        if (moving)
                        {
                            pointList.Last().Add(new Point(x, y));
                        }
                        else
                        {
                            pointList.Add(new List<Point>() { new Point(x, y) });
                        }

                        moving = true;

                        mat.Circle(x, y, 1, color, 3, LineType.AntiAlias);

                        window.ShowImage(mat);

                    }
                    else if (e == MouseEvent.MouseMove && flags == MouseEvent.FlagLButton)
                    {
                        if (moving)
                        {

                            pointList.Last().Add(new Point(x, y));

                            // 点を削除
                            pointList.RemoveAll(list => list.Count <= 1);

                            mat.Polylines(pointList, false, color, 3, LineType.AntiAlias);
                        }
                        else
                        {
                            pointList.Add(new List<Point>() { new Point(x, y) });
                        }
                        moving = true;

                        window.ShowImage(mat);
                    }
                    else if (e == MouseEvent.LButtonUp)
                    {
                        moving = false;
                    }
                };

                bool notEscDown = true;
                while (notEscDown)
                {
                    switch (Cv2.WaitKey(1))
                    {
                        case 3014656: //Delete #Clear
                            pointList.Clear();
                            pointList.Add(new List<Point>());
                            mat.SetTo(new Scalar(255, 255, 255));
                            window.ShowImage(mat);
                            break;
                        case 27: //Esc #Exit
                            notEscDown = false;
                            break;
                        case 32: //SpaceBar #Save
                            mat.SaveImage(DateTime.Now.ToString("yyyyMMdd-HHmmss") + ".jpg");
                            break;
                        default:
                            break;
                    }
                }
            }
        }
    }
}