Previously, third-party components must be used to implement thumbnails on the page. Now, with. NET, you can easily implement thumbnails. The following is an example of how to implement a thumbnail.
Keywords: C #, ASP. NET, thumbnail
Download instance: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 = "percent" %>
<Html>
<Head>
<Title> Lion interactive network => generating thumbnails </title>
</Head>
<Body>
<Form id = "Form1" method = "post" runat = "server">
</Form>
</Body>
</Html>
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 of ToThumbnailImage.
/// </Summary>
Public class ToThumbnailImage: System. Web. UI. Page
{
/*
Create By lion
Copyright (C) 2004 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 by region Web Form 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 the method for generating thumbnails
ToThumbnailImages ("lionsky.jpg", "B .gif", 300 );
}
# Endregion
# Region Helper
/// <Summary>
/// Obtain all relevant information of the image decoder
/// </Summary>
/// <Param name = "mimeType"> a string containing the multi-purpose Internet Mail Extension protocol (MIME) of the decoder </param>
/// <Returns> returns all information about the image decoder. </returns>
Static ImageCodecInfo GetCodecInfo (string mimeType)
{
ImageCodecInfo [] CodecInfo = ImageCodecInfo. GetImageEncoders ();
Foreach (ImageCodecInfo ici in CodecInfo)
{
If (ici. MimeType = mimeType) return ici;
}
Return null;
}
/// <Summary>
/// Check the validity of the extension
/// </Summary>
/// <Param name = "sExt"> file name extension </param>
/// <Returns> If the extension is valid, true is returned; otherwise, false is returned. </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 the image
/// </Summary>
/// <Param name = "image"> Image object </param>
/// <Param name = "savePath"> Save path </param>
/// <Param name = "ici"> codec parameters in the specified format </param>
Void SaveImage (System. Drawing. Image image, string savePath, ImageCodecInfo ici)
{
// Set the EncoderParameters object of the original image 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 a thumbnail
/// </Summary>
/// <Param name = "sourceImagePath"> original image path (relative path) </param>
/// <Param name = "thumbnailImagePath"> the generated thumbnail path. If it is null, save it as the original image path (relative path). </param>
/// <Param name = "thumbnailImageWidth"> width of the thumbnail (the height is automatically generated based on the proportion of the source image) </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 format of the original image file is incorrect. supported formats include [" + AllowExt + "]", "SourceImagePath ");
}
// Create an Image object from the original Image
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 image proportion
If (double) width)/(double) height)> = 1.33333333333333f)
{
Num = (height * ThumbnailImageWidth)/width );
}
Else
{
ThumbnailImageWidth = (width * num)/height );
}
If (ThumbnailImageWidth <1) | (num <1 ))
{
Return;
}
// Initialize a new Bitmap instance with the specified size and format
Bitmap bitmap = new Bitmap (ThumbnailImageWidth, num, PixelFormat. Format32bppArgb );
// Create a new Graphics object from the specified Image object
Graphics graphics = Graphics. FromImage (bitmap );
// Clear the entire drawing surface and fill it with a transparent background color
Graphics. Clear (Color. Transparent );
// Draw the original image object at the specified position and by the specified size
Graphics. DrawImage (image, new Rectangle (0, 0, ThumbnailImageWidth, num ));
Image. Dispose ();
Try
{
// Save the original image in the specified format and use 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
}
}
Source: http://blog.csdn.net/houjianxun/archive/2004/07/07/aaaaa.aspx
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