Ihttphandler Image Watermark

The ihttphandler principle has been described in the article "ihttphandler URL rewriting". If you do not understand it, refer to this document.Article.

This document describes how to watermark a website image. The same principle lies in the configuration of Web. config and the GDI + operation.

First, configure web. config as follows:

<Httphandlers>
<Add verb = "*" Path = "*. jpg" type = "myhttphandler. watermarkhandler, myhttphandler"/>

For the same reason, see the article "ihttphandler URL rewriting". When the path is "* .jpg.pdf, for example, “logo.gif", it is processed by myhttphandler. watermarkhandler and then returned to the client.

Let's take a look at the implementation of watermarkhandler:

Using System;
Using System. Collections. Generic;
Using System. text;
Using System. Web;
Using System. drawing;
Using System. Drawing. imaging;
Using System. IO;

namespace myhttphandler
{< br> class watermarkhandler: ihttphandler
{< br> # region ihttphandler member

Public bool isreusable
{< br> Get { return true ;}
}

Public VoidProcessrequest (httpcontext context)
{
Commondeal. dealimagerequest (context );
}

# Endregion
}
}

The implementation of commondeal is as follows:

 

Using System;
Using System. Collections. Generic;
Using System. text;
Using System. Web;
Using System. Web. UI;
Using System. IO;
Using System. drawing;
Using System. Drawing. imaging;

Namespace Myhttphandler
{
Internal   Class Commondeal
{
Public   Static   Void Dealimagerequest (httpcontext context)
{
Font enfont =   New Font ( " Times New Roman " , 12 );

Memorystream MS= NewMemorystream ();

String Filepath = Context. server. mappath ( " Image "   + Context. Request. Path );
Try
{
Image = Image. fromfile (filepath );
If (Ispixelformatindexed (image. pixelformat ))
{
Bitmap BMP =   New Bitmap (image. Width, image. Height, pixelformat. format32bppargb );
Using (Graphics graphic = Graphics. fromimage (BMP ))
{
Graphic. interpolationmode = System. Drawing. drawing2d. interpolationmode. highqualitybicubic;
Graphic. smoothingmode = System. Drawing. drawing2d. smoothingmode. highquality;
Graphic. compositingquality = System. Drawing. drawing2d. compositingquality. highquality;
Graphic. drawimage (image, 0 , 0 );
Graphic. drawstring ( " Pangxiaoliang " , Enfont, New Solidbrush (color. lightgray ), 2 , 2 );
Graphic. drawstring ( " Pangxiaoliang " , Enfont, New Solidbrush (color. Black ), 0 , 0 );

}
BMP. Save (MS, system. Drawing. imaging. imageformat. GIF );
BMP. Dispose ();
}
Else
{
Using (Graphics graphic = Graphics. fromimage (image ))
{
Graphic. drawstring ( " Pangxiaoliang " , Enfont, New Solidbrush (color. lightgray ), 2 , 2 );
Graphic. drawstring ( " Pangxiaoliang " , Enfont, New Solidbrush (color. Black ), 0 , 0 );

}

bitmap thebitmap = New Bitmap (image );
thebitmap. save (MS, system. drawing. imaging. imageformat. JPEG);
thebitmap. dispose ();
}

Context. response. clearcontent ();
Context. response. contenttype= "Image/jpg";
Context. response. binarywrite (Ms. toarray ());

}
Catch
{
Bitmap Error =   New Bitmap (context. server. mappath ( " Image/error.bmp " ));
Error. Save (MS, system. Drawing. imaging. imageformat. JPEG );
Error. Dispose ();
Context. response. clearcontent ();
Context. response. contenttype =   " Image/jpg " ;
Context. response. binarywrite (Ms. toarray ());
}
Finally
{
Ms. Close ();
Ms. Dispose ();
Context. response. End ();
}
}

Public   Static   Void Returnerrorimage (httpcontext context)
{
Memorystream MS =   New Memorystream ();
Try
{
Bitmap Error =   New Bitmap (context. server. mappath ( " Error.bmp " ));
Error. Save (MS, system. Drawing. imaging. imageformat. JPEG );
Error. Dispose ();
Context. response. clearcontent ();
Context. response. contenttype =   " Image/jpg " ;
Context. response. binarywrite (Ms. toarray ());
}
Catch
{
}
Finally
{
Ms. Close ();
Ms. Dispose ();
Context. response. End ();
}
}

///   <Summary>
/// The pixelformat of the graphics exception is generated.
///   </Summary>
Private   Static Pixelformat [] indexedpixelformats = {Pixelformat. undefined, pixelformat. dontcare,
Pixelformat. format16bppargb1555, pixelformat. format1bppindexed, pixelformat. format4bppindexed,
Pixelformat. format8bppindexed
};

///   <Summary>
/// Determines whether the pixelformat of the image is in the pixelformat that causes an exception.
///   </Summary>
///   <Param name = "imgpixelformat"> Pixelformat of the original image </Param>
///   <Returns> </returns>
Private   Static   Bool Ispixelformatindexed (pixelformat imgpixelformat)
{
Foreach (Pixelformat pf In Indexedpixelformats)
{
If (PF. Equals (imgpixelformat )) Return   True ;
}
Return   False ;
}
}

}

 

 

1) string filepath = context. server. mappath ("image" + context. Request. Path); first obtain the absolute path of the image on the server, so that the image can be processed.

2) memorystream MS = new memorystream (); memory stream is used to respond to client requests and return the processed image to the client.

3) Use GDI + to write a name on the image and return the new image to the client as a stream.