APS.NET上传图使之缩小

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html文件

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

<!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>在ASP.NET里轻松实现缩略图</title>
    <meta content="Microsoft Visual Studio.NET 7.0" name="GENERATOR">
    <meta content="Visual Basic 7.0" name="CODE_LANGUAGE">
    <meta content="JavaScript" name="vs_defaultClientScript">
    <meta content="http://schemas.microsoft.com/intellisense/ie5" name="vs_targetSchema">
</HEAD>
<body MS_POSITIONING="GridLayout">
       <form id="Form1" method="post" runat="server" enctype="multipart/form-data">
      <INPUT type="file" name="file" width="600"><br>
          <asp:Button ID="Button1" runat="server" Text="Button" /><br>
           <asp:Label ID="Label1" runat="server" Text="Label"></asp:Label>
    </form>
</body>

</html>

cs文件:

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;
using System.Drawing.Imaging;

public partial class Thumbnail : System.Web.UI.Page
{

    private void Page_Load(object sender, System.EventArgs e)
    {
        // 在此处放置用户代码以初始化页面
        Label1.Text = "<h3>在ASP.NET里轻松实现缩略图</h3>";
        Button1.Text = "上载并显示缩略图";

}

    #region Web 窗体设计器生成的代码
    override protected void OnInit(EventArgs e)
    {
        //
        // CODEGEN: 该调用是 ASP.NET Web 窗体设计器所必需的。
        //
        InitializeComponent();
        base.OnInit(e);
    }

    /// <summary>
    /// 设计器支持所需的方法 - 不要使用代码编辑器修改
    /// 此方法的内容。
    /// </summary>
    private void InitializeComponent()
    {
        this.Button1.Click += new System.EventHandler(this.Button1_Click);
        this.Load += new System.EventHandler(this.Page_Load);

}
#endregion

    private void Button1_Click(object sender, System.EventArgs e)
    {
        HttpFileCollection MyFileColl = HttpContext.Current.Request.Files;
        HttpPostedFile MyPostedFile = MyFileColl[0];

        if (MyPostedFile.ContentType.ToString().ToLower().IndexOf("image") < 0)
        {
            Response.Write("无效的图形格式。");
            return;
        }
        GetThumbNail(MyPostedFile.FileName, 100, 100, MyPostedFile.ContentType.ToString(), false, MyPostedFile.InputStream);
    }
    private System.Drawing.Imaging.ImageFormat GetImageType(object strContentType)
    {
        if ((strContentType.ToString().ToLower()) == "image/pjpeg")
        {
            return System.Drawing.Imaging.ImageFormat.Jpeg;
        }
        else if ((strContentType.ToString().ToLower()) == "image/gif")
        {
            return System.Drawing.Imaging.ImageFormat.Gif;
        }
        else if ((strContentType.ToString().ToLower()) == "image/bmp")
        {
            return System.Drawing.Imaging.ImageFormat.Bmp;
        }
        else if ((strContentType.ToString().ToLower()) == "image/tiff")
        {
            return System.Drawing.Imaging.ImageFormat.Tiff;
        }
        else if ((strContentType.ToString().ToLower()) == "image/x-icon")
        {
            return System.Drawing.Imaging.ImageFormat.Icon;
        }
        else if ((strContentType.ToString().ToLower()) == "image/x-png")
        {
            return System.Drawing.Imaging.ImageFormat.Png;
        }
        else if ((strContentType.ToString().ToLower()) == "image/x-emf")
        {
            return System.Drawing.Imaging.ImageFormat.Emf;
        }
        else if ((strContentType.ToString().ToLower()) == "image/x-exif")
        {
            return System.Drawing.Imaging.ImageFormat.Exif;
        }
        else if ((strContentType.ToString().ToLower()) == "image/x-wmf")
        {
            return System.Drawing.Imaging.ImageFormat.Wmf;
        }
        else
        {
            return System.Drawing.Imaging.ImageFormat.MemoryBmp;
        }
    }

    private void GetThumbNail(string strFileName, int iWidth, int iheight,string strContentType, bool blnGetFromFile, System.IO.Stream ImgStream)
    {
        System.Drawing.Image oImg;

        if (blnGetFromFile)
        {
            oImg = System.Drawing.Image.FromFile(strFileName);
        }
        else
        {
            oImg = System.Drawing.Image.FromStream(ImgStream);
        }
        oImg = oImg.GetThumbnailImage(iWidth, iheight, null, IntPtr.Zero);
        string strGuid = System.Guid.NewGuid().ToString().ToUpper();
        string strFileExt = strFileName.Substring(strFileName.LastIndexOf("."));

        //保存到本地
        string charS = "//";
        oImg.Save(Server.MapPath("uploadImg") +charS+ strGuid + strFileExt, GetImageType(strContentType));
        //直接输出URL
        Response.Redirect("uploadImg/" + strGuid+strFileExt);
        //以下显示在屏幕上
        Response.ContentType = strContentType;
        MemoryStream MemStream = new MemoryStream();
        //注意：这里如果直接用 oImg.Save(Response.OutputStream, GetImageType(strContentType))
        //对不同的格式可能会出错，比如Png格式。
        oImg.Save(MemStream, GetImageType(strContentType));
        MemStream.WriteTo(Response.OutputStream);
    }

}