C#のWinFormsで画像加工アプリ12「Cannyフィルタで境界線抽出」

using OpenCvSharp;
using OpenCvSharp.Extensions;

namespace GazouKakou02;
public partial class Form1 : Form
{
    // メニュー項目
    readonly ToolStripMenuItem cannyMenuItem = new()
    {
        Text = "Cannyフィルタ",
    };
    
    /// <summary>
    /// Cannyフィルタの初期化
    /// </summary>
    public void Init_Canny()
    {
        // メニューの登録
        filterMenuItem.DropDownItems.Add(cannyMenuItem);

        // フィルター（Cannyフィルタ）
        Func<Bitmap, double, double, Task<Bitmap>> filter = new(async (src, threshold1, threshold2) =>
        {
            return await Task.Run(()=>
            {
                using Mat srcMat = BitmapConverter.ToMat(src);
                using Mat dstMat = new();

                Cv2.Canny(srcMat, dstMat, threshold1, threshold2);

                return BitmapConverter.ToBitmap(dstMat);
            });
        });

        // メニューアイテムのクリックイベント
        cannyMenuItem.Click += (s, e) =>
        {
            if (_buffBmp is null) return;

            var dialog = new FilterDialog();

            dialog.Load += (s, e) =>
            {
                dialog.Track1.Maximum = 5000;
                dialog.Track1.Minimum = 1;
                dialog.Track1.Value = 50;
            };

            bool filterFlag = false;
            dialog.OkBtn.Enabled = !filterFlag;
            Bitmap? bmp = null;
            dialog.Track1.ValueChanged += async (s, e) =>
            {
                dialog.Track1Label.Text = string.Format("th:{0}", (double)dialog.Track1.Value / 10.0d);
                if (filterFlag)
                {
                    // フィルター実行中につきキャンセル
                    return;
                }

                filterFlag = true;
                var backupValue = dialog.Track1.Value;
                var currentValue = backupValue;
                do
                {
                    backupValue = currentValue;

                    double th = (double)currentValue / 10;
                    bmp = await filter(_buffBmp, th, th);
                    dialog.Picbox.Image?.Dispose();
                    dialog.Picbox.Image = bmp;

                    currentValue = dialog.Track1.Value;
                } while( currentValue != backupValue);

                filterFlag = false;
                dialog.OkBtn.Enabled = !filterFlag;
            };

            if (dialog.ShowDialog() == DialogResult.OK)
            {
                // OK
                this.Bmp = bmp;
            } else {
                // Cancel
                bmp?.Dispose();
            }
        };
    }
}