Before thumbnails, implementing thumbnails on a page must be aided by Third-party components. Now that you have. NET, you can easily implement thumbnails. Here is an example of implementing a thumbnail.
Keywords: C #, ASP.net, thumbnails
Instance Download: http://www.lionsky.net/MyWebSite/DownSoft/list.aspx?id=221
Tothumbnailimage.aspx
<%@ Page language= "C #" codebehind= "ToThumbnailImage.aspx.cs" src= "ToThumbnailImage.aspx.cs" autoeventwireup= " False "inherits=" Exam_c.tothumbnailimage "%>
<title>lion Interactive network => generate thumbnails </title>
<body>
<form id= "Form1" method= "POST" runat= "Server" >
</form>
</body>
ToThumbnailImage.aspx.cs
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.Drawing.Imaging;
Namespace Exam_c
{
<summary>
Summary description of the tothumbnailimage.
</summary>
public class ToThumbnailImage:System.Web.UI.Page
{
/*
Create by Lion
2003-05-20 19:00
Copyright (C) www.LionSky.Net. All rights reserved.
Web:http://www.lionsky.net;
Email:lion-a@sohu.com
*/
Static Hashtable htmimes=new Hashtable ();
Internal ReadOnly string allowext = ". jpe|. Jpeg|. Jpg|. Png|. Tif|. Tiff|. BMP ";
Code generated #region the Web forms Designer
Override protected void OnInit (EventArgs e)
{
#region htmimes[". Jpe"]= "Image/jpeg";
htmimes[". jpeg"]= "image/jpeg";
htmimes[". jpg"]= "image/jpeg";
htmimes[". png"]= "image/png";
htmimes[". tif"]= "Image/tiff";
htmimes[". Tiff"]= "Image/tiff";
htmimes[". bmp"]= "image/bmp";
#endregion
Call Generation Thumbnail method
Tothumbnailimages ("Lionsky.jpg", "B.gif", 300);
}
#endregion
#region Helper
<summary>
Get all the relevant information about the image codec
</summary>
<param name= "MimeType" > A Multipurpose Internet Mail Extension Protocol (MIME) type containing codecs </param>
<returns> return all relevant information about the image codec </returns>
Static ImageCodecInfo Getcodecinfo (String mimetype)
{
imagecodecinfo[] Codecinfo = Imagecodecinfo.getimageencoders ();
foreach (ImageCodecInfo ici in codecinfo)
{
if (ICI. MimeType = = mimetype) return ici;
}
return null;
}
<summary>
Detecting the validity of an extension
</summary>
<param name= "SEXT" > FileName extension </param>
<returns> returns True if the extension is valid, otherwise returns false.</returns>
BOOL Checkvalidext (String sExt)
{
BOOL Flag=false;
string[] Aext = allowext.split (' | ');
foreach (string filetype in aext)
{
if (filetype. ToLower () ==sext)
{
Flag = true;
Break
}
}
return flag;
}
<summary>
Save picture
</summary>
<param name= "image" >image object </param>
<param name= "Savepath" > Save path </param>
<param name= "ICI" > specified format for codec parameters </param>
void SaveImage (System.Drawing.Image image,string savepath,imagecodecinfo ici)
{
Set the EncoderParameters object for the original picture object
EncoderParameters parameters = new EncoderParameters (1);
Parameters. Param[0] = new Encoderparameter (Encoder.quality, ((Long) 90));
Image. Save (Savepath, ICI, parameters);
Parameters. Dispose ();
}
#endregion
#region Methods
<summary>
Generate thumbnails
</summary>
<param name= "Sourceimagepath" > Original image Path (relative path) </param>
<param name= "Thumbnailimagepath" > The resulting thumbnail path, if empty, save as the original picture path (relative path) </param>
<param name= "Thumbnailimagewidth" > Thumbnail width (height is automatically generated by the proportion of the source picture) </param>
public void Tothumbnailimages (string sourceimagepath,string thumbnailimagepath,int thumbnailimagewidth)
{
string sourceimagepath = Sourceimagepath;
string thumbnailimagepath = Thumbnailimagepath;
int thumbnailimagewidth = Thumbnailimagewidth;
String sExt = Sourceimagepath.substring (Sourceimagepath.lastindexof (".")). ToLower ();
if (sourceimagepath.tostring () ==system.string.empty) throw new NullReferenceException ("Sourceimagepath is null!");
if (! Checkvalidext (SEXT))
{
throw new ArgumentException ("The original picture file format is not correct, the support format has [" + Allowext + "]", "Sourceimagepath");
}
Create an Image object from the original picture
System.Drawing.Image Image = System.Drawing.Image.FromFile (HttpContext.Current.Server.MapPath (Sourceimagepath));
int num = ((THUMBNAILIMAGEWIDTH/4) * 3);
int width = image. Width;
int height = image. Height;
Calculate the proportions of a picture
if (((double)/((double) height) >= 1.3333333333333333f)
{
num = ((height * thumbnailimagewidth)/width);
}
Else
{
Thumbnailimagewidth = ((width * num)/height);
}
if ((Thumbnailimagewidth < 1) | | (num < 1))
{
Return
}
Initializes a new instance of the Bitmap class with the specified size and format
Bitmap Bitmap = new Bitmap (thumbnailimagewidth, num, Pixelformat.format32bppargb);
Creates a new Graphics object from the specified Image object
Graphics Graphics = graphics.fromimage (bitmap);
Clear the entire drawing surface and fill with a transparent background color
Graphics. Clear (color.transparent);
Draws the original picture object at the specified location and at the specified size
Graphics. DrawImage (Image, new Rectangle (0, 0, thumbnailimagewidth, num));
Image. Dispose ();
Try
{
Saves the original picture in the specified format and with the specified codec parameter to the specified file
String Savepath = (thumbnailimagepath==null? Sourceimagepath:thumbnailimagepath);
SaveImage (Bitmap,httpcontext.current.server.mappath (Savepath), Getcodecinfo ((String) htmimes[sext));
}
catch (System.Exception e)
{
Throw e;
}
Finally
{
Bitmap. Dispose ();
Graphics. Dispose ();
}
}
#endregion
}
}
