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());

     }

 }