以前，在页面上实现缩略图必须借助第三方组件。现在，有了.NET，就可以很轻松地实现缩略图。下面就是实现缩略图的例子。
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" 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 ThumbnailClass 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#Region " Web Form Designer Generated Code " 'This call is required by the Web Form Designer. <System.Diagnostics.DebuggerStepThrough()> Private Sub InitializeComponent()Sub InitializeComponent()
End Sub Private Sub Page_Init()Sub Page_Init(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Init 'CODEGEN: This method call is required by the Web Form Designer 'Do not modify it using the code editor. InitializeComponent() End Sub#End Region Private Sub Page_Load()Sub Page_Load(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles MyBase.Load 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" End Sub Private Sub Button1_Click()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("无效的图形格式。") Exit Sub End If GetThumbNail(MyPostedFile.FileName, 100, 100, MyPostedFile.ContentType.ToString(),_ False, MyPostedFile.InputStream) End Sub Private Function GetImageType()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()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)) '直接输出url文件 'Response.Redirect("images/" + strGuid + strFileExt) '以下显示在屏幕上 Response.ContentType = strContentType Dim MemStream As 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) 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#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); }