在ASP.NET里轻松实现缩略图

简介: 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 http://dotnet.aspx.cc/Exam/Thumbnail.
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
http://dotnet.aspx.cc/Exam/Thumbnail.aspx

代码如下:Thumbnail.aspx

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<%@ 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

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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

C#
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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";
}

#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);
}
/// <summary>
        /// 设计器支持所需的方法 - 不要使用代码编辑器修改
        /// 此方法的内容。
        /// </summary>
        private void InitializeComponent()
{
this.Button1.Click += new System.EventHandler(this.Button1_Click);
this.Load += new System.EventHandler(this.Page_Load);
}
        #endregion

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("无效的图形格式。");
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);
}
}
}
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