Previously, the thumbnail on the page must be used to use a third party component. Now, with .NET, thumbnails can be easily implemented. Below is an example of achieving thumbnails.
Keywords: C #, ASP.NET, thumbnail
Example 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"%>
Lion Interactive Network => Generates Thumbnail </ Title></p>
<p></ hEAD></p>
<p><body></p>
<p><form id = "form1" method = "post" runat = "server"></p>
<p></ form></p>
<p></ body></p>
<p></ html></p>
<p>TOTHUMBNAILIMAGE.ASPX.CS</p>
<p>Using system;</p>
<p>Using system.collections;</p>
<p>Using system.componentmodel;</p>
<p>Using system.data;</p>
<p>Using system.drawing;</p>
<p>Using system.Web;</p>
<p>Using system.Web.SessionState;</p>
<p>Using system.Web.ui;</p>
<p>Using system.Web.ui.webcontrols;</p>
<p>Using system.Web.ui.htmlcontrols;</p>
<p>Using system.drawing.image;</p>
<p>Namespace Exam_C</p>
<p>{</p>
<p>/// <summary></p>
<p>/// TothumbnailImage's summary description.</p>
<p>/// </ summary></p>
<p>Public Class TothumbnailImage: System.Web.ui.page</p>
<p>{</p>
<p>/ *</p>
<p>Create by Lion</p>
<p>2003-05-20 19:00</p>
<p>Copyright (c) 2004 www.lionsky.net. All Rights Reserved.</p>
<p>Web: http://www.lionsky.net;</p>
<p>Email: lion-a@sohu.com</p>
<p>* /</p>
<p>Static hashtable htmimes = new hashtable ();</p>
<p>INTERNAL READONLY STRING ALLOWEXT = ".jpe | .jpeg | .jpg | .png | .tif | .tiff | .bmp";</p>
<p>#Region web form designer generated code</p>
<p>Override protected void oninit (Eventargs E)</p>
<p>{</p>
<p>#Region htmimes [". JPE"] = "image / jpeg";</p>
<p>HTMIMES ["JPEG"] = "image / jpeg";</p>
<p>HTMIMES ["JPG"] = "image / jpeg";</p>
<p>HTMIMES ["PNG"] = "image / png";</p>
<p>HTMIMES [". TIF"] = "image / TIFF"; htmimes [". TIFF"] = "image / TIFF";</p>
<p>HTMIMES [". BMP"] = "image / bmp";</p>
<p>#ndregion</p>
<p>// Call generation thumbnail method</p>
<p>TOTHUMBNAILIMAGES ("Lionsky.jpg", "B.GIF", 300);</p>
<p>}</p>
<p>#ndregion</p>
<p>#Region Helper</p>
<p>/// <summary></p>
<p>/// Get all related information of the image codec</p>
<p>/// </ summary></p>
<p>/// <param name = "mimetype"> String </ param> containing the multi-purpose Internet mail expansion protocol (MIME) type encoding decoder</p>
<p>/// <returns> Returns all related information of the image codec </ returns></p>
<p>Static ImageCodecInfo getCodecInfo (String MimeType)</p>
<p>{</p>
<p>ImageCodecInfo [] CODECINFO = ImageCodecInfo.getImageEncoders ();</p>
<p>FOREACH (ImageCodecInfo ICI in CodecInfo)</p>
<p>{</p>
<p>Ici.mimetype == mimetype) Return ICI;</p>
<p>}</p>
<p>Return NULL;</p>
<p>}</p>
<p>/// <summary></p>
<p>/// Detect the validity of the extension</p>
<p>/// </ summary></p>
<p>/// <param name = "sext"> File name extension </ param></p>
<p>/// <returns> Returns true if the extension is valid, otherwise returns false. </ returns></p>
<p>Bool CheckValidext (String Sext)</p>
<p>{</p>
<p>Bool flag = false;</p>
<p>String [] ate = allowext.split ('|');</p>
<p>FOREACH (String FileType in axt)</p>
<p>{</p>
<p>IF (filetype.tolower () == sext)</p>
<p>{</p>
<p>Flag = true;</p>
<p>Break;</p>
<p>}</p>
<p>}</p>
<p>Return flag;</p>
<p>}</p>
<p>/// <summary></p>
<p>/// save Picture</p>
<p>/// </ summary></p>
<p>/// <param name = "image"> image object </ param></p>
<p>/// <param name = "savepath"> Save Path </ param></p>
<p>/// <param name = "ici"> The codec parameter of the specified format </ param></p>
<p>Void SaveImage (System.drawing.Image Image, String SavePath, ImageCodecInfo ICI)</p>
<p>{</p>
<p>/ / Set an EncoderParameters object for the original image object</p>
<p>Encoderparameters parameters = new encoderparameters (1);</p>
<p>Parameters.Param [0] = New ENCODERPARETER (Encoder.quality, ((long) 90));</p>
<p>Image.save (SavePath, ICI, Parameters);</p>
<p>Parameters.dispose ();</p>
<p>}</p>
<p>#ndregion</p>
<p>#Region Methods</p>
<p>/// <summary> /// Generate thumbnails</p>
<p>/// </ summary></p>
<p>/// <param name = "SourceImagePath"> Original image path (relative path) </ param></p>
<p>/// <param name = "thumbnailimagePath"> The generated thumbnail path, save it as the original picture path (relative path) </ param></p>
<p>/// <param name = "thumbnailimageWidth"> The width of the thumbnail (high degree and pressing image proportion) </ param></p>
<p>Public void TothumbnailImages (String SourceImagePath, Int thumbnailimagewidth)</p>
<p>{</p>
<p>String sourceImagePath = sourceImagepath;</p>
<p>String thumbnailimagePath = thumbnailimagepath;</p>
<p>Int thumbnailimagewidth = thumbnailimagewidth;</p>
<p>String sext = sourceImagePath.Substring (SourceImagePath.lastIndexof (".")). TOLOWER ();</p>
<p>IF (SourceImagePath.Tostring () == System.String.empty) Throw new nullreferenceException ("SourceImagePath is Null!");</p>
<p>IF (! Checkvalidext (sext))</p>
<p>{</p>
<p>Throw new ArgumentException ("The original image file format is incorrect, the supported format has [" allowext "]", "SourceImagePath");</p>
<p>}</p>
<p>// Create an image object from the original picture</p>
<p>System.drawing.Image image = system.drawing.image.fromfile (httpcontext.current.server.mappath (sourceImagePath);</p>
<p>INT NUM = ((ThumbnailimageWidth / 4) * 3);</p>
<p>Int width = image.width;</p>
<p>INT height = image.height;</p>
<p>/ / Calculate the proportion of pictures</p>
<p>IF ((Double) Width / (Double) Height)> = 1.3333333F)</p>
<p>{</p>
<p>Num = (Height * thumbnailimagewidth) / width);</p>
<p>}</p>
<p>Else</p>
<p>{</p>
<p>ThumbnailimageWidth = (width * num) / height;</p>
<p>}</p>
<p>IF ((ThumbnailImageWidth <1) || (Num <1))</p>
<p>{</p>
<p>Return;</p>
<p>}</p>
<p>// initialize new instances of Bitmap classes with the specified size and format</p>
<p>Bitmap Bitmap = New Bitmap (thumbnailimageWidth, Num, Pixelformat.Format32bppargb);</p>
<p>/ / Create a new Graphics object from the specified image object</p>
<p>Graphics graphics = graphics.fromimage (bitmap);</p>
<p>/ / Clear the entire drawing and fill in transparent background</p>
<p>Graphics.clear (color.Transparent); // Draw the original image object in the specified position and press the specified size</p>
<p>Graphics.drawImage (Image, New Rectangle (0, 0, ThumbnailImageWidth, Num);</p>
<p>Image.dispose ();</p>
<p>Try</p>
<p>{</p>
<p>/ / Save this original image in a specified format and saved to the specified file with the specified codec parameter</p>
<p>String SavePath = (thumbnailimagePath == NULL? SourceImagePath: thumbnailimagePath);</p>
<p>SaveImage (Bitmap, httpcontext.current.server.mappath (savepath), getCodecInfo ((String) htmimes [sext]);</p>
<p>}</p>
<p>Catch (System.exception E)</p>
<p>{</p>
<p>Throw e;</p>
<p>}</p>
<p>Finally</p>
<p>{</p>
<p>Bitmap.dispose ();</p>
<p>Graphics.dispose ();</p>
<p>}</p>
<p>}</p>
<p>#ndregion</p>
<p>}</p>
<p>}</p></div><div class="text-center mt-3 text-grey">
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var jmessage_width = Math.min(jdiv.width(), maxwidth);
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var img_height = this.org_height;
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