Dynamic Webcam Image

• Download project & COM Server - 166 Kb

Contents

• Introduction
• Method
• Usage
• Conclusion
• Faced Problems

Introduction

This project presents the way to dynamically generate a picture with C# and ASP.NET. Basically a browser points to your page and gets back a picture grabbed on your webcam.

You will be able to access your webcam by placing a HTML IMG tag on your webpage. The picture at the top is an example of usage.

To be able to use the webcam you need to register with regsvr32 the COM Dll CamServer.dll in the 'COM Component' directory.

Method

The first thing to do to get a picture from an ASP.NET page is to determine the MIME file type that the file will handle. In our case the MIME type is JPEG. So we define in the ContentType of the Page:

<%@ Page Language="c#" ContentType="image/jpeg" %>

We also need to specify at the top of the page the namespace that will be used:

<%@ Import Namespace="System" %>
<%@ Import Namespace="System.IO" %>
<%@ Import Namespace="System.Drawing" %>
<%@ Import Namespace="System.Drawing.Drawing2D" %>
<%@ Import Namespace="System.Drawing.Imaging" %>
<%@ Import Namespace="System.Net" %>

Then comes the code that will grab the image from the wbecam and returns it to the client:

<script language="C#" runat="server">

protected void Page_Load(object sender, EventArgs e)
{
    //Jpeg compression quality
    short nQuality = 45;

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

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

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

    Graphics g = Graphics.FromImage( bmp );

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

	StringFormat drawFormat = new StringFormat();
    drawFormat.Alignment = StringAlignment.Center;

    g.DrawString(   strDate,
                    new Font( FontFamily.GenericSansSerif, 12 ),
                    new SolidBrush( Color.Black ), 
                    new RectangleF( 1,1,320,240 ),
                    drawFormat
                );

    g.DrawString(   strDate,
                    new Font( FontFamily.GenericSansSerif, 12 ),
                    new SolidBrush( Color.White ), 
                    new RectangleF( 0,0,320,240 ),
                    drawFormat
                );

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

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

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

    bmp.Save( Response.OutputStream, icf[1], encps );
    
    g.Dispose();
    bmp.Dispose();
}
</script>

In the code there is nothing new, compared to the other articles. We get a jpeg picture grabbed by the webcam using COM Interop. We add the hour and the little difference is that the image stream is saved to Response.OutputStream .

Usage

You may reference the ASP.NET page has a normal jpeg picture:

<img src="http://XXX/WebcamPicture/WebForm1.aspx" width="320" height="240"/>

or in a ASP:Image control.

Conclusion

This opens lots of possibilities in the creation of dynamic graphics. For example you may create dynamic charts linked to database values returned has a normal graphic in a presentation page. You may also make easily a visit counter for your pages...

Known Issues

• None.

History

Version 1.00

June 14, 2002 First release.