В свободной форме выделения с#

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Здравствуйте, я работаю над этим проектом, который мне нужно обрезать из picturebox выбор свободной формы, а затем сохранить новое изображение.

У меня есть этот код, который сохраняет мои загруженные фотографии в папку, которая, если ее не существует, создает ее.

private void button1_Click(object sender, EventArgs e)
        {

            ++NumberOfClick;
            switch (NumberOfClick)
            {
                case 1:
                    OpenFileDialog f = new OpenFileDialog();
                    f.Filter = "Image files (*.jpg, *.jpeg, *.jpe, *.jfif, *.png) | *.jpg; *.jpeg; *.jpe; *.jfif; *.png";

                    if (f.ShowDialog() == DialogResult.OK)
                    {
                        File = Image.FromFile(f.FileName);
                        pictureBox1.Image = File;
                    }

                    pictureBox1.Image.Save(@"C:\Users\User\Desktop\Gallery\image1.png", ImageFormat.Png);

                    DialogResult result = MessageBox.Show("Do you want to crop this image?", "Confirmation", MessageBoxButtons.YesNo);

                    if(result == DialogResult.Yes)
                    {
                        
                        pictureBox5.Visible = true;
                        button1.Visible = false;
                        pictureBox5.Image = pictureBox1.Image;

                    }

                    

                    break;
                case 2:
                    OpenFileDialog f2 = new OpenFileDialog();
                    f2.Filter = "Image files (*.jpg, *.jpeg, *.jpe, *.jfif, *.png) | *.jpg; *.jpeg; *.jpe; *.jfif; *.png";

                    if (f2.ShowDialog() == DialogResult.OK)
                    {
                        File = Image.FromFile(f2.FileName);
                        pictureBox2.Image = pictureBox1.Image;
                        pictureBox1.Image = File;
                    }

                    pictureBox1.Image.Save(@"C:\Users\User\Desktop\Gallery\image2.png", ImageFormat.Png);

                    break;
                case 3:
                    OpenFileDialog f3 = new OpenFileDialog();
                    f3.Filter = "Image files (*.jpg, *.jpeg, *.jpe, *.jfif, *.png) | *.jpg; *.jpeg; *.jpe; *.jfif; *.png";

                    if (f3.ShowDialog() == DialogResult.OK)
                    {
                        File = Image.FromFile(f3.FileName);
                        pictureBox3.Image = pictureBox2.Image;
                        pictureBox2.Image = pictureBox1.Image;
                        pictureBox1.Image = File;
                    }

                    pictureBox1.Image.Save(@"C:\Users\User\Desktop\Gallery\image3.png", ImageFormat.Png);

                    break;
                case 4:
                    OpenFileDialog f4 = new OpenFileDialog();
                    f4.Filter = "Image files (*.jpg, *.jpeg, *.jpe, *.jfif, *.png) | *.jpg; *.jpeg; *.jpe; *.jfif; *.png";

                    if (f4.ShowDialog() == DialogResult.OK)
                    {
                        File = Image.FromFile(f4.FileName);
                        pictureBox4.Image = pictureBox3.Image;
                        pictureBox3.Image = pictureBox2.Image;
                        pictureBox2.Image = pictureBox1.Image;
                        pictureBox1.Image = File;
                    }

                    pictureBox1.Image.Save(@"C:\Users\User\Desktop\Gallery\image4.png", ImageFormat.Png);

                    break;
                default:

                    OpenFileDialog f5 = new OpenFileDialog();
                    f5.Filter = "Image files (*.jpg, *.jpeg, *.jpe, *.jfif, *.png) | *.jpg; *.jpeg; *.jpe; *.jfif; *.png";

                    if (f5.ShowDialog() == DialogResult.OK)
                    {
                        File = Image.FromFile(f5.FileName);

                        File.Save(@"C:\Users\User\Desktop\Gallery\image" + NumberOfClick.ToString() + ".png", ImageFormat.Png);
                        
                        pictureBox4.Image = pictureBox3.Image;
                        pictureBox3.Image = pictureBox2.Image;
                        pictureBox2.Image = pictureBox1.Image;
                        pictureBox1.Image = File;
                    }

                        break;
            }
        }

Что я уже пробовал:

Я уже сделал прямоугольную обрезку, но мне нужен этот выбор свободной формы..

Вот мой прямоугольник обрезки:

Image img;
	bool mouseClicked;
	Point startPoint = new Point();
	Point endPoint = new Point();

	Rectangle rectCropArea;

	private void Button1_Click(System.Object sender, System.EventArgs e)
	{
	}

	private void OnLoad(System.Object sender, System.EventArgs e)
	{
		loadPrimaryImage();
	}

	private void loadPrimaryImage()
	{
		img = Image.FromFile("..\\..\\images.jpg");
		PictureBox1.Image = img;
	}

	private void PicBox_MouseUp(System.Object sender, System.Windows.Forms.MouseEventArgs e)
	{
		mouseClicked = false;
		if ((endPoint.X != -1)) {
			Point currentPoint = new Point(e.X, e.Y);
			Y1.Text = e.X.ToString();
			Y2.Text = e.Y.ToString();
		}

		endPoint.X = -1;
		endPoint.Y = -1;
		startPoint.X = -1;
		startPoint.Y = -1;
	}

	private void PicBox_MouseDown(System.Object sender, System.Windows.Forms.MouseEventArgs e)
	{
		mouseClicked = true;
		startPoint.X = e.X;
		startPoint.Y = e.Y;
		//Display coordinates
		X1.Text = startPoint.X.ToString();
		Y1.Text = startPoint.Y.ToString();

		endPoint.X = -1;
		endPoint.Y = -1;

		rectCropArea = new Rectangle(new Point(e.X, e.Y), new Size());
	}

	private void PicBox_MouseMove(System.Object sender, System.Windows.Forms.MouseEventArgs e)
	{
		Point ptCurrent = new Point(e.X, e.Y);


		if ((mouseClicked)) {
			if ((endPoint.X != -1)) {
				//Display Coordinates
				X1.Text = startPoint.X.ToString();
				Y1.Text = startPoint.Y.ToString();
				X2.Text = e.X.ToString();
				Y2.Text = e.Y.ToString();
			}

			endPoint = ptCurrent;

			if ((e.X > startPoint.X & e.Y > startPoint.Y)) {
				rectCropArea.Width = e.X - startPoint.X;
				rectCropArea.Height = e.Y - startPoint.Y;


			} else if ((e.X < startPoint.X & e.Y > startPoint.Y)) {
				rectCropArea.Width = startPoint.X - e.X;
				rectCropArea.Height = e.Y - startPoint.Y;
				rectCropArea.X = e.X;
				rectCropArea.Y = startPoint.Y;

			} else if ((e.X > startPoint.X & e.Y < startPoint.Y)) {
				rectCropArea.Width = e.X - startPoint.X;
				rectCropArea.Height = startPoint.Y - e.Y;
				rectCropArea.X = startPoint.X;
				rectCropArea.Y = e.Y;

			} else {
				rectCropArea.Width = startPoint.X - e.X;
				rectCropArea.Height = startPoint.Y - e.Y;
				rectCropArea.X = e.X;
				rectCropArea.Y = e.Y;
			}

			PictureBox1.Refresh();

		}

	}

	private void PicBox_Paint(System.Object sender, System.Windows.Forms.PaintEventArgs e)
	{
		Pen drawLine = new Pen(Color.Red);
		drawLine.DashStyle = DashStyle.Dash;
		e.Graphics.DrawRectangle(drawLine, rectCropArea);
	}

	private void btnCrop_Click(System.Object sender, System.EventArgs e)
	{
		PictureBox2.Refresh();

		Bitmap sourceBitmap = new Bitmap(PictureBox1.Image, PictureBox1.Width, PictureBox1.Height);
		Graphics g = PictureBox2.CreateGraphics();

		if (!(CheckBox1.Checked)) {
			g.DrawImage(sourceBitmap, new Rectangle(0, 0, PictureBox2.Width, PictureBox2.Height), rectCropArea, GraphicsUnit.Pixel);
			sourceBitmap.Dispose();

		} else {
			int x1 = 0;
			int x2 = 0;
			int y1 = 0;
			int y2 = 0;
			try {
				x1 = Convert.ToInt32(CX1.Text);
				x2 = Convert.ToInt32(CX2.Text);
				y1 = Convert.ToInt32(CY1.Text);
				y2 = Convert.ToInt32(CY2.Text);
			} catch (Exception ex) {
				MessageBox.Show("Enter valid Coordinates (only Integer values)");
			}

			if (((x1 < x2 & y1 < y2))) {
				rectCropArea = new Rectangle(x1, y1, x2 - x1, y2 - y1);
			} else if ((x2 < x1 & y2 > y1)) {
				rectCropArea = new Rectangle(x2, y1, x1 - x2, y2 - y1);
			} else if ((x2 > x1 & y2 < y1)) {
				rectCropArea = new Rectangle(x1, y2, x2 - x1, y1 - y2);
			} else {
				rectCropArea = new Rectangle(x2, y2, x1 - x2, y1 - y2);
			}

			PictureBox1.Refresh();
			//This repositions the dashed box to new location as per coordinates entered.

			g.DrawImage(sourceBitmap, new Rectangle(0, 0, PictureBox2.Width, PictureBox2.Height), rectCropArea, GraphicsUnit.Pixel);
			sourceBitmap.Dispose();
		}
	}

	private void pictureBox1_MouseClick(System.Object sender, System.Windows.Forms.MouseEventArgs e)
	{
		PictureBox1.Refresh();
	}

	private void CheckBox1_CheckedChanged(System.Object sender, System.EventArgs e)
	{
		if ((CheckBox1.Checked)) {
			CX1.Visible = true;
			Label10.Visible = true;
			CY1.Visible = true;
			Label9.Visible = true;
			CX2.Visible = true;
			Label8.Visible = true;
			CY2.Visible = true;
			Label7.Visible = true;

			X1.Text = "0";
			X2.Text = "0";
			Y1.Text = "0";
			Y2.Text = "0";

		} else {
			CX1.Visible = false;
			Label10.Visible = false;
			CY1.Visible = false;
			Label9.Visible = false;
			CX2.Visible = false;
			Label8.Visible = false;
			CY2.Visible = false;
			Label7.Visible = false;
		}

	}
	public Form1()
	{
		Load += OnLoad;
	}
}

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