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在ASP.NET里轻松实现缩略图_0

发布时间:2019-09-12 11:16:19

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。

查看例子

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.vb

Imports System

Imports System.Web

Imports System.Drawing

Imports System.IO

Imports 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

#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 Sub

End Class

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