如何将图形保存为png或jpg文件c#

using System;
using System.Drawing;
using System.Drawing.Imaging;

class Program
{
    static void Main()
    {
        // 创建Bitmap对象
        Bitmap bitmap = new Bitmap(500, 500, PixelFormat.Format32bppArgb);

        // 创建Graphics对象
        using (Graphics graphics = Graphics.FromImage(bitmap))
        {
            // 绘制图形
            graphics.DrawLine(Pens.Red, 0, 0, 100, 100);
            graphics.DrawRectangle(Pens.Blue, 50, 50, 200, 100);
            graphics.DrawEllipse(Pens.Green, 100, 100, 200, 200);
        }

        // 保存为PNG文件
        bitmap.Save("image.png", ImageFormat.Png);

        // 保存为JPG文件
        bitmap.Save("image.jpg", ImageFormat.Jpeg);
    }
}