在ASP.NET中上传图片并生成缩略图的C#源码 <FONT size=4><FONT size=4><FONT size=4>using System;
using System.Collections;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Web;
using System.Web.SessionState;
using System.Web.UI;
using System.Web.UI.WebControls;
using System.Web.UI.HtmlControls;
using System.IO;
using System.Drawing.Imaging;

namespace eMeng.Exam
{
/// <summary>
/// Thumbnail 的摘要说明。
/// </summary>
public class Thumbnail : System.Web.UI.Page
{
protected System.Web.UI.WebControls.Label Label1;
protected System.Web.UI.WebControls.Button Button1;

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里轻松实炙趼酝?lt;/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("."));
Response.ContentType = strContentType;
MemoryStream MemStream = new MemoryStream();
oImg.Save(MemStream, GetImageType(strContentType));
MemStream.WriteTo(Response.OutputStream);
}

}
}
</FONT></FONT></FONT><FONT color=#ff0000 size=4></FONT><FONT size=4>功能：
1。把图片文件(JPG GIF PNG)上传，
2。保存到指定的路径（在web.config中设置路径，以文件的原有格式保存），
3。并自动生成指定宽度的（在web.config中设置宽度）
4。和指定格式的（在web.config中指定缩略图的格式）
5。和原图比例相同的缩略图(根据宽度和原图的宽和高计算所略图的高度)
6。可以判断是否已经存在文件
7。如果不覆盖，则给出错误
8。如果选中"覆盖原图"checkbox，则覆盖原图。
9。可以根据要求，在webform上设置1个以上的file input和相应的checkbox
10。并在文件上传完毕后，显示原图的文件名，尺寸，字节，和
11。缩略图的文件名尺寸。
12。缩略图的文件名格式：原图+"_thumb."+指定格式，如：test.jpg_thumb.gif,以便于管理。

--------------------
public void UploadFile(object sender, System.EventArgs e)
{

string imgNameOnly, imgNameNoExt, imgExt;
string imgThumbnail;
int erroNumber = 0;
System.Drawing.Image oriImg, newImg;
string strFePicSavePath = ConfigurationSettings.AppSettings["FePicSavePath"].ToString();
string strFePicThumbFormat = ConfigurationSettings.AppSettings["FePicThumbFormat"].ToString().ToLower();
int intFeThumbWidth = Int32.Parse(ConfigurationSettings.AppSettings["FePicThumbWidth"]);
string fileExt;

StringBuilder picInfo = new StringBuilder();

if(Page.IsValid)
{

for(int i = 0;i < Request.Files.Count; i++)
{
HttpPostedFile PostedFile = Request.Files[i];
fileExt = (System.IO.Path.GetExtension(PostedFile.FileName)).ToString().ToLower();

imgNameOnly = System.IO.Path.GetFileName(PostedFile.FileName);
if(fileExt == ".jpg" || fileExt == ".gif" || fileExt == ".png")
{

if(System.IO.File.Exists(strFePicSavePath + imgNameOnly) && (checkboxlistRewrite.Items[i].Selected == false))
{
erroNumber = erroNumber + 1;
picInfo.Append("<b>错误：</b>文件("+ (i+1) +") " + imgNameOnly + " 已经存在，请修改文件名<br/>" );
}
}
else
{
erroNumber = erroNumber + 1;
picInfo.Append("<b>错误：</b>文件("+ (i+1) +") " + imgNameOnly + " 扩展名 " + fileExt + " 不被许可<br/>" );
}

}

if(erroNumber > 0)
{
picInfo.Append("<font color=red>全部操作均未完成，请修改错误，再进行操作</font><br/>");
}
else
{
for(int i = 0;i < Request.Files.Count; i++)
{

HttpPostedFile PostedFile = Request.Files[i];
imgNameOnly = System.IO.Path.GetFileName(PostedFile.FileName);
imgNameNoExt = System.IO.Path.GetFileNameWithoutExtension(PostedFile.FileName);
imgExt = System.IO.Path.GetExtension(PostedFile.FileName).ToString().ToLower();

oriImg = System.Drawing.Image.FromStream(PostedFile.InputStream);
newImg = oriImg.GetThumbnailImage(intFeThumbWidth, intFeThumbWidth * oriImg.Height/oriImg.Width,null,new System.IntPtr(0));
switch(imgExt)
{
//case ".jpeg":
case ".jpg":
oriImg.Save(strFePicSavePath + imgNameOnly , System.Drawing.Imaging.ImageFormat.Jpeg);
break;
case ".gif":
oriImg.Save(strFePicSavePath + imgNameOnly , System.Drawing.Imaging.ImageFormat.Gif);
break;
case ".png":
oriImg.Save(strFePicSavePath + imgNameOnly , System.Drawing.Imaging.ImageFormat.Png);
break;
}

//oriImg.Save(ConfigurationSettings.AppSettings["FePicSavePath"] + imgNameNoExt + ".jpg", System.Drawing.Imaging.ImageFormat.Jpeg);

switch(strFePicThumbFormat)
{
//jpeg format can get the smallest file size, and the png is the largest size
//case "jpeg":
case "jpg":
newImg.Save(strFePicSavePath + imgNameOnly + "_thumb.jpg",System.Drawing.Imaging.ImageFormat.Jpeg);
imgThumbnail = imgNameOnly + "_thumb.jpg";
break;
case "gif":
newImg.Save(strFePicSavePath + imgNameOnly + "_thumb.gif",System.Drawing.Imaging.ImageFormat.Gif);
imgThumbnail = imgNameOnly + "_thumb.gif";
break;
case "png":
newImg.Save(strFePicSavePath + imgNameOnly + "_thumb.png",System.Drawing.Imaging.ImageFormat.Png);
imgThumbnail = imgNameOnly + "_thumb.png";
break;
default:
newImg.Save(strFePicSavePath + imgNameOnly + "_thumb.jpg",System.Drawing.Imaging.ImageFormat.Jpeg);
imgThumbnail = imgNameOnly + "_thumb.jpg";
break;

}//switch

picInfo.Append("<b>文件　名：</b>" + imgNameOnly + " ( " + oriImg.Width + " x " + oriImg.Height + " ) " + PostedFile.ContentLength/1024 + "KB<br/>");
picInfo.Append("<b>缩略图名：</b>" + imgThumbnail + " ( " + newImg.Width + " x " + newImg.Height + " )<br/><br/>");

oriImg.Dispose();
newImg.Dispose();

}//for
picInfo.Append("<font color=red>所有操作成功</font><br/>");

}// if erronumber = 0

}
else
{
picInfo.Append("<font color=red>有错误，请检查。操作未成功</font><br/>");

}

lblPicInfo.Text = picInfo.ToString();

}
</FONT>