以前，在頁面上實現縮略圖必須藉助第三方組件。現在，有了.NET，就可以很輕鬆地實現縮略圖。下面就是實現縮略圖的例子。
Thumbnail.aspx
<%@ Page Language="vb" AutoEventWireup="false" Codebehind="Thumbnail.aspx.vb" Inherits="aspxWeb.Thumbnail" %><!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.0 Transitional//EN"><HTML> <HEAD> <title>在ASP.NET裏輕鬆實現縮略圖</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" runat="server" enctype="multipart/form-data"> <INPUT type="file" name="file" width="600"><br><br> <asp:Button id="Button1" runat="server"></asp:Button> </form> </body></HTML>Thumbnail.aspx.vb
Imports SystemImports System.WebImports System.DrawingImports System.IOImports System.Drawing.Imaging
Public Class Thumbnail
Inherits System.Web.UI.Page Protected WithEvents Label1 As System.Web.UI.WebControls.Label Protected WithEvents Button1 As System.Web.UI.WebControls.Button
Web Form Designer Generated Code
Private Sub Page_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load Label1.Text = "<h3>在ASP.NET裏輕鬆實現縮略圖</h3>" Button1.Text = "上載並顯示縮略圖"
End Sub Private Sub Button1_Click(ByVal sender As Object, ByVal e As System.EventArgs) Handles Button1.Click Dim MyFileColl As HttpFileCollection = HttpContext.Current.Request.Files Dim MyPostedFile As HttpPostedFile = MyFileColl.Item(0) If LCase(MyPostedFile.ContentType.ToString()).IndexOf("image") < 0 Then Response.Write("無效的圖形格式。") Exit Sub End If GetThumbNail(MyPostedFile.FileName, 100, 100, MyPostedFile.ContentType.ToString(),_ False, MyPostedFile.InputStream) End Sub Private Function GetImageType(ByVal strContentType) As System.Drawing.Imaging.ImageFormat Select Case (strContentType.ToString().ToLower()) Case "image/pjpeg" GetImageType = System.Drawing.Imaging.ImageFormat.Jpeg Case "image/gif" GetImageType = System.Drawing.Imaging.ImageFormat.Gif Case "image/bmp" GetImageType = System.Drawing.Imaging.ImageFormat.Bmp Case "image/tiff" GetImageType = System.Drawing.Imaging.ImageFormat.Tiff Case "image/x-icon" GetImageType = System.Drawing.Imaging.ImageFormat.Icon Case "image/x-png" GetImageType = System.Drawing.Imaging.ImageFormat.Png Case "image/x-emf" GetImageType = System.Drawing.Imaging.ImageFormat.Emf Case "image/x-exif" GetImageType = System.Drawing.Imaging.ImageFormat.Exif Case "image/x-wmf" GetImageType = System.Drawing.Imaging.ImageFormat.Wmf Case Else GetImageType = System.Drawing.Imaging.ImageFormat.MemoryBmp End Select End Function Private Sub GetThumbNail(ByVal strFileName, ByVal iWidth, ByVal iheight, ByVal strContentType, _ ByVal blnGetFromFile, ByVal ImgStream) Dim oImg As Image If blnGetFromFile Then oImg = oImg.FromFile(strFileName) Else oImg = oImg.FromStream(ImgStream) End If oImg = oImg.GetThumbnailImage(iWidth, iheight, Nothing, (New IntPtr()).Zero) Dim strGuid As String = (New Guid()).NewGuid().ToString().ToUpper() Dim strFileExt As String = strFileName.Substring(strFileName.LastIndexOf(".")) '保存到本地 'oImg.Save(Server.MapPath("images") + "" + strGuid + strFileExt, GetImageType(strContentType)) '直接輸出url文件 'Response.Redirect("images/" + strGuid + strFileExt) '以下顯示在屏幕上 Response.ContentType = strContentType Dim MemStream As New MemoryStream() ' 注意：這裏如果直接用 oImg.Save(Response.OutputStream, GetImageType(strContentType)) ' 對不同的格式可能會出錯，比如Png格式。 oImg.Save(MemStream, GetImageType(strContentType)) MemStream.WriteTo(Response.OutputStream) End Sub
End ClassC#
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 的摘要說明。/// </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) { // 在此處放置用戶代碼以初始化頁面 Label1.Text = "<h3>在ASP.NET裏輕鬆實現縮略圖</h3>"; Button1.Text = "上載並顯示縮略圖"; } Web 窗體設計器生成的代碼 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("無效的圖形格式。"); 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); } }}點擊查看演示。該代碼在vs.2003中調試成功!