Examples of C # implementation thumbnails

C # language has a lot to learn, here we mainly introduce C # implementation thumbnails, including the introduction of C # Implementation thumbnails must rely on third-party components and so on.

In the past, C # implementation thumbnails on the page had to rely on third-party components. Now, with. NET, you can easily implement thumbnails in C #.

The following is an example of a C # implementation thumbnail.

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 ";





#region The code generated by 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>





///gets all the relevant information about the image codec


///


</summary>





///


<param


name= "MimeType"


>


A string of Multipurpose Internet Mail Extension Protocol (MIME) types containing codecs


</param>





///


<returns>


returns 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>





///to detect the validity of the 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"


>


the encoding and decoding parameters for the specified format


</param>





void SaveImage (System.Drawing.Image image,string savepath,imagecodecinfo ici)


{


//Set the EncoderParameters object of 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 picture path (relative path)


</param>





///


<param


name= "Thumbnailimagepath"


>


the resulting thumbnail path,


Save As the original picture path (relative path) if empty


</param>





///


<param


name= "Thumbnailimagewidth"


>


the width of the thumbnail (the 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 incorrect, the support format has [" + Allowext + "]", "Sourceimagepath");


}


//Create image object from 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 the picture


if (((double) width)/((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);


//Clears the entire drawing surface and fills with a transparent background color


Graphics. Clear (color.transparent);


//At the specified location and draw the original picture object 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





}


}