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Webcam Web Service

, 13 May 2002
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ASP.NET Web Service written in C# to grab a picture from a webcam
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Contents

Introduction

C# Webcam is a port to ASP.NET and C# of the C++ ATL Web Service. It demonstrates the ease of use of C# and ASP.NET to build Web Services compared to ATL Server Web Service.

The project is still based on the Webcam COM component developed in the C++ ATL Web Service. .NET COM Interop is used to import it in the C# project.

Web Service

With Visual Studio, create a new C# ASP.NET Web Service project. Add a reference to 'CamServer 1.0 Type Library' on the COM tab. If 'CamServer 1.0 Type Library' is not in the list, you need to register the Dll CamServer.dll in the 'COM Components' directory. Add this Web Method to the source code obtained by the wizard:

[WebMethod]
public byte[] GrabFrame( short nQuality )
{
    //Shoot a picture from my webcam
    CAMSERVERLib.Camera cam = new CAMSERVERLib.CameraClass();

    return (byte[])cam.GrabFrame( nQuality );
}
Compared to the C++ ATL Web Service we need only three lines of code to get the picture from the COM component and return it to the client.

To have a little more fun coding I decided to add some features. Now it writes to the Windows EventLog the IP and the name of the machine calling it, after a DNS resolution. I have also added the date and hour of the local computer directly in the picture. And at last it increments a system performance counter to keep an eye on the number of people calling it.
[WebMethod]
public byte[] GrabFrame( short nQuality )
{
    //Write to the EventLog the IP and Host name
    string addr = HttpContext.Current.Request.UserHostAddress.Trim();

    string name;

    IPHostEntry host = null;

    try
    {
        host = System.Net.Dns.GetHostByAddress( addr );

        if ( host != null )
        {
            name = host.HostName;
            for( int i = 0; i < host.Aliases.Length; i++ )
                name += "*" + host.Aliases[i];

            eventLog.WriteEntry( addr + " : " + name );
        }
        else
        {
            name = "ERROR";

            eventLog.WriteEntry( name );
        }
    }
    catch( System.Exception error )
    {
        // process the error error.Message
    }

    //Shoot a picture from my webcam
    CAMSERVERLib.Camera cam = new CAMSERVERLib.CameraClass();

    byte[] picture = (byte[])cam.GrabFrame( nQuality );

    //Increments Performance Counter
    performanceCounterShoot.Increment();

    //Add the hour
    MemoryStream ms = new MemoryStream( picture );
    Bitmap bmp = new Bitmap( ms );

    Graphics g = Graphics.FromImage( bmp );

    string strDate = DateTime.Now.ToLongDateString() + 
                     " - " + 
                     DateTime.Now.ToLongTimeString(); 

    g.DrawString(   strDate,
                    new Font( FontFamily.GenericSansSerif, 10 ),
                    new SolidBrush( Color.Black ), 
                    new RectangleF( 1,1,320,240 ) 
                );

    g.DrawString(   strDate,
                    new Font( FontFamily.GenericSansSerif, 10 ),
                    new SolidBrush( Color.White ), 
                    new RectangleF( 0,0,320,240 ) 
                );

    MemoryStream ms2 = new MemoryStream();

    //Get codecs
    ImageCodecInfo[] icf = ImageCodecInfo.GetImageEncoders();

    EncoderParameters encps = new EncoderParameters( 1 );
    EncoderParameter encp = new EncoderParameter( Encoder.Quality, (long) nQuality );

    //Set quality
    encps.Param[0] = encp;

    bmp.Save( ms2, icf[1], encps );
    ms2.Close();

    return ms2.ToArray();
}

Client

The client ActiveX has no need to be modified. It is just needed to change the url of the Web Service, that is now:
http://YOUR_IP/webcamcsharp/service1.asmx?WSDL

Don't forget to register with regsvr32.exe the AxCamClient.dll in the 'COM Components' directory.

Conclusion

With few lines of source code you may obtain the same result then with little more C++ work.

The solution may be better because the COM component pack the picture, we unpack it to add date and hour then we pack again the new picture to send back to the client.

Problems Faced 

  • None.

History

Version 1.00 April 10, 2002
First release.

License

This article has no explicit license attached to it but may contain usage terms in the article text or the download files themselves. If in doubt please contact the author via the discussion board below.

A list of licenses authors might use can be found here

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About the Author

Laurent Kempé
Architect
France France

Laurent Kempé is the editor, founder, and primary contributor of Tech Head Brothers, a French portal about Microsoft .NET technologies.

He is currently employed by Innoveo Solutions since 10/2007 as a Senior Solution Architect and certified Scrum Master.

Founder, owner and Managing Partner of Jobping, which provides a unique and efficient platform for connecting Microsoft skilled job seekers with employers using Microsoft technologies.

Laurent is awarded by Microsoft since Avril 2002: Most Valuable Professional (MVP).

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Comments and Discussions

 
QuestionGrabFrame error Pinmemberinternational ninja28-Sep-11 11:16 

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