用于绘画应用程序的可定制的椭圆

我一直在用C＃绘制应用程序。 我想添加一个选项来切换用当前画笔绘制椭圆。 我一直在困难如何使它的椭圆的大小和Y位置变化，而按住鼠标。 有任何想法吗？ 这是我的代码。

using System; using System.Collections.Generic; using System.ComponentModel; using System.Data; using System.Drawing; using System.Linq; using System.Text; using System.Threading.Tasks; using System.Windows.Forms; namespace ZSPainter { public partial class Form1 : Form { string drawToolString; Graphics g; bool c = false; bool drawEllipse = false; Point sp = new Point(0, 0); Point ep = new Point(0, 0); Pen p = new Pen(Color.Black, 1); Brush b = new SolidBrush(Color.Black); public Form1() { InitializeComponent(); } private void penToolStripMenuItem_Click(object sender, EventArgs e) { drawToolString = "pen"; toolString.Text = "Current Tool: Pen"; } private void brushToolStripMenuItem_Click(object sender, EventArgs e) { drawToolString = "brush"; toolString.Text = "Current Tool: Brush"; } private void Form1_MouseDown(object sender, MouseEventArgs e) { sp = e.Location; if(e.Button == MouseButtons.Left) c = true; } private void Form1_MouseMove(object sender, MouseEventArgs e) { if (drawToolString == "pen" && c) { ep = e.Location; g = this.CreateGraphics(); if(!drawEllipse) g.DrawLine(p, sp, ep); /*else * *------Here is where I want an ellipse to drawn if drawEllipse is true.------ */ } else if (drawToolString == "brush" && c) { ep = e.Location; g = this.CreateGraphics(); if(!drawEllipse) g.DrawLine(new Pen(b, 3), sp, ep); /*else * *------Here is where I want an ellipse to drawn if drawEllipse is true.------ */ } sp = ep; } private void Form1_MouseUp(object sender, MouseEventArgs e) { c = false; } private void ellipse_Click(object sender, EventArgs e) { drawEllipse = !drawEllipse; } } }