想将网上的一幅图片转存到成缩略图到服务器，在线给分。。
比如：网上一幅图http://www.hpp888.net/UploadFile/2005-5/20055119118681.jpg


想通过一个函数的转存到服务器上，形成　高100×宽100　的缩略图，请高手指点思路和方法。。

------解决方案--------------------
HttpWebRequest
------解决方案--------------------
HttpWebResponse resp;
HttpWebRequest req = (HttpWebRequest)HttpWebRequest.Create( "http://www.csdn.net/Images/logo_csdn.gif ");
req.Timeout = 150000;
resp = (HttpWebResponse)req.GetResponse();
System.Drawing.Image img;
img = new System.Drawing.Bitmap(resp.GetResponseStream());
//--获取
//--保存缩微图 可以用下面的类
using System;
using System.Data;
using System.Configuration;
using System.Web;
using System.Web.Security;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.WebControls.WebParts;
using System.Web.UI.HtmlControls;
using System.Drawing;

/// <summary>
/// MicroImage 的摘要说明
/// </summary>
public sealed class MicroImage
{
private MicroImage()
{
}

/// <summary>
/// 生成缩略图
/// </summary>
/// <param name= "originalImagePath "> 源图路径（物理路径） </param>
/// <param name= "thumbnailPath "> 缩略图路径（物理路径） </param>
/// <param name= "width "> 缩略图宽度 </param>
/// <param name= "height "> 缩略图高度 </param>
/// <param name= "mode "> 生成缩略图的方式 </param>
public static void MakeThumbnail(string originalImagePath, string thumbnailPath, int width, int height, string mode)
{
System.Drawing.Image originalImage = System.Drawing.Image.FromFile(originalImagePath);

int towidth = width;
int toheight = height;

int x = 0;
int y = 0;
int ow = originalImage.Width;
int oh = originalImage.Height;

switch (mode)
{
case "HW "://指定高宽缩放（可能变形）
break;
case "W "://指定宽，高按比例
toheight = originalImage.Height * width / originalImage.Width;
break;
case "H "://指定高，宽按比例
towidth = originalImage.Width * height / originalImage.Height;
break;
case "Cut "://指定高宽裁减（不变形）
if ((double)originalImage.Width / (double)originalImage.Height > (double)towidth / (double)toheight)
{
oh = originalImage.Height;
ow = originalImage.Height * towidth / toheight;
y = 0;
x = (originalImage.Width - ow) / 2;
}
else
{
ow = originalImage.Width;
oh = originalImage.Width * height / towidth;
x = 0;
y = (originalImage.Height - oh) / 2;
}
break;
default:
break;
}

//新建一个bmp图片
System.Drawing.Image bitmap = new System.Drawing.Bitmap(towidth, toheight);

//新建一个画板
Graphics g = System.Drawing.Graphics.FromImage(bitmap);

//设置高质量插值法
g.InterpolationMode = System.Drawing.Drawing2D.InterpolationMode.High;

//设置高质量,低速度呈现平滑程度