<% @ Page Language="C#" AutoEventWireup="true" CodeFile="upfile.aspx.cs" Inherits="upfile_upfile"  %>

<! DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd" >

< html  xmlns ="http://www.w3.org/1999/xhtml"   >
< head  runat ="server" >
     < title > 无标题页 </ title >
</ head >
< body >
     < form  id ="form1"  runat ="server" >
     < div >
         < asp:FileUpload  ID ="FileUpload1"  runat ="server"   />
         < asp:Button  ID ="Button1"  runat ="server"  OnClick ="Button1_Click"  Text ="上传"   />< br  />
         < asp:Label  ID ="Label1"  runat ="server" ></ asp:Label ></ div >
     </ form >
</ body >
</ html >

using  System;
using  System.Data;
using  System.Configuration;
using  System.Collections;
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.IO;

public  partial  class  upfile_upfile : System.Web.UI.Page
{
    protected void Page_Load(object sender, EventArgs e)
    {

    }
    protected void Button1_Click(object sender, EventArgs e)
    {
        if (FileUpload1.HasFile)
        {
            string fileContentType = FileUpload1.PostedFile.ContentType;
            if (fileContentType == "image/bmp" || fileContentType == "image/gif" || fileContentType == "image/pjpeg")
            {
                string name = FileUpload1.PostedFile.FileName;                  // 客户端文件路径

                FileInfo file = new FileInfo(name);
                string fileName = file.Name;                                    // 文件名称
                string fileName_s = "s_" + file.Name;                             // 缩略图文件名称
                string webFilePath = Server.MapPath("file/" + fileName);        // 服务器端文件路径
                string webFilePath_s = Server.MapPath("file/" + fileName_s);　　// 服务器端缩略图路径

                if (!File.Exists(webFilePath))
                {
                    try
                    {
                        FileUpload1.SaveAs(webFilePath);                                // 使用 SaveAs 方法保存文件
                        MakeThumbnail(webFilePath, webFilePath_s, 130, 130, "Cut");     // 生成缩略图方法
                        Label1.Text = "提示：文件“" + fileName + "”成功上传，并生成“" + fileName_s + "”缩略图，文件类型为：" + FileUpload1.PostedFile.ContentType + "，文件大小为：" + FileUpload1.PostedFile.ContentLength + "B";
                    }
                    catch (Exception ex)
                    {
                        Label1.Text = "提示：文件上传失败，失败原因：" + ex.Message;
                    }
                }
                else
                {
                    Label1.Text = "提示：文件已经存在，请重命名后上传";
                }
            }
            else
            {
                Label1.Text = "提示：文件类型不符";
            }
        }
    }
    /**//// <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
        System.Drawing.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
        g.SmoothingMode = System.Drawing.Drawing2D.SmoothingMode.HighQuality;

        //清空画布并以透明背景色填充
        g.Clear(System.Drawing.Color.Transparent);

        //在指定位置并且按指定大小绘制原图片的指定部分
        g.DrawImage(originalImage, new System.Drawing.Rectangle(0, 0, towidth, toheight),
            new System.Drawing.Rectangle(x, y, ow, oh),
            System.Drawing.GraphicsUnit.Pixel);

        try
        {
            //以jpg格式保存缩略图
            bitmap.Save(thumbnailPath, System.Drawing.Imaging.ImageFormat.Jpeg);
        }
        catch (System.Exception e)
        {
            throw e;
        }
        finally
        {
            originalImage.Dispose();
            bitmap.Dispose();
            g.Dispose();
        }
    }
}