前台代码:
<%@ Page language="c#" Codebehind="TestWebForm.aspx.cs" AutoEventWireup="false" Inherits="Example.TestWebForm" %><!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"><HTML> <HEAD> <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"> <asp:label id="Label1" runat="server"></asp:label> <form id="Form1" method="post" encType="multipart/form-data" runat="server"> <INPUT type="file" name="file" width="600"><br> <br> <asp:Button id="Button1" runat="server"></asp:Button></form> </body></HTML>
后台代码:
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 Example
{
/// <summary>
/// TestWebForm 的摘要说明。
/// </summary> public class TestWebForm : 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里轻松实现缩略图</h3>"; Button1.Text = "上载并显示缩略图"; }
Web 窗体设计器生成的代码 private void Button1_Click(object sender, System.EventArgs e) { HttpFileCollection MyFileColl = HttpContext.Current.Request.Files; //获取客户端上载的文件（多部件 MIME 格式）集合 HttpPostedFile MyPostedFile = MyFileColl[0]; //获取第一个文件 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); } /// <summary> /// 得到图片的类型 /// </summary> /// <param name="strContentType"></param> /// <returns></returns> 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; } } /// <summary> /// 得到缩略图 /// </summary> /// <param name="strFileName">文件名</param> /// <param name="iWidth">宽度</param> /// <param name="iheight">高度</param> /// <param name="strContentType"></param> /// <param name="blnGetFromFile">是否从文件创建Image对象</param> /// <param name="ImgStream"></param> 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); //GetThumbnailImage方法是返回此Image对象的缩略图 string strGuid = System.Guid.NewGuid().ToString().ToUpper(); //初始化 Guid 类的新实例 string strFileExt = strFileName.Substring(strFileName.LastIndexOf(".")); //得到图片的后缀 Response.ContentType = strContentType; MemoryStream MemStream = new MemoryStream(); //创建其支持存储区为内存的流 oImg.Save(MemStream, GetImageType(strContentType)); MemStream.WriteTo(Response.OutputStream); //WriteTo方法是将此内存流的整个内容写入另一个流中 } }
}
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