asp.net GDI+ 使用PathGradienBrush类实现彩色渐变

 using System;
 using System.Collections.Generic;
 using System.Linq;
 using System.Web;
 using System.Web.UI;
 using System.Web.UI.WebControls;
 using System.Drawing;
 using System.Drawing.Drawing2D;

 public partial class _Default : System.Web.UI.Page
 {
     protected void Page_Load(object sender, EventArgs e)
     {
         Bitmap bitmap = new Bitmap(, );
         Graphics graphics = Graphics.FromImage(bitmap);
         graphics.Clear(Color.White);
         Point centerPoint = new Point(, );
         int r = ;
         GraphicsPath path = new GraphicsPath();
         path.AddEllipse(centerPoint.X - r, centerPoint.Y - r,  * r,  * r);
         PathGradientBrush mypathgradientBrush = new PathGradientBrush(path);
         mypathgradientBrush.CenterPoint = centerPoint;
         mypathgradientBrush.CenterColor = Color.DarkGreen;
         mypathgradientBrush.SurroundColors = new Color[] { Color.Gold };
         graphics.FillEllipse(mypathgradientBrush, centerPoint.X - r, centerPoint.Y - r,  * r,  * r);
         centerPoint = new Point(, );
         r = ;
         path = new GraphicsPath();
         path.AddEllipse(centerPoint.X - r, centerPoint.Y - r,  * r,  * r);
         path.AddEllipse(centerPoint.X - *r, centerPoint.Y - *r,  * r,  * r);
         path.AddEllipse(centerPoint.X -  * r, centerPoint.Y -  * r,  * r,  * r);
         mypathgradientBrush = new PathGradientBrush(path);
         mypathgradientBrush.CenterPoint = centerPoint;
         mypathgradientBrush.CenterColor = Color.Gold;
         mypathgradientBrush.SurroundColors = new Color[] { Color.Black, Color.Blue, Color.DarkGreen };
         graphics.FillPath(mypathgradientBrush, path);
         System.IO.MemoryStream ms = new System.IO.MemoryStream();
         bitmap.Save(ms, System.Drawing.Imaging.ImageFormat.Jpeg);
         Response.ClearContent();
         Response.ContentType = "image/Jpeg";
         Response.BinaryWrite(ms.ToArray());
     }
 }