在ASP.NET里轻松实现缩略图
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。
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代码如下：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 > 后代码：Thumbnail.aspx.vbImports SystemImports System.WebImports System.DrawingImports System.IOImports System.Drawing.ImagingPublic 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#Region " Web Form Designer Generated Code " 'This call is required by the Web Form Designer. < System .Diagnostics.DebuggerStepThrough() > Private Sub InitializeComponent() End Sub Private 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(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(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(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 SubEnd Class