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Webcam32 Image Update


Once a web page has been written in HTML which includes an image which has been uploaded by Webcam32, the page will unfortunately be static.  As new images are uploaded by Webcam32, they will not automatically cause the page to be refreshed.   This guide demonstrates a number of different techniques to achieve an image refresh and see a new picture.

There are a number of different options available to refresh an image in a page:


Meta Refresh

The meta refresh mechanism is the simplest technique.  By including the following tag in the 


		
The content value specifies the number of seconds after which the page should completely reload.  Since most of the page is already in the browsers cache, the only time consuming component will be the part which has changed, this should only be the Webcam32 uploaded image.

		
The down-side of this simple technique is that the whole page will appear to flicker.   For a professional looking page, this technique may be too simple but is a good and quick technique for testing.

		
The Meta Refresh technique may be used inside an HTML frame to only refresh a portion of the page. This is more complex and will still cause the image to appear to flash or flicker as it is reloaded.

		
This technique is known to work with all browsers including Microsoft Internet Explorer and Netscape Navigator.

		

		

		

		

		
JavaCam applet

		
Webcam32 has an optional downloadable Java application called JavaCam.  The purpose of JavaCam is to automatically reload an image from the Webserver every interval and refresh the image.  The image is displayed within a Java applet and there is no screen flicker or page refresh at all.  JavaCam works with both Netscape and Microsoft browsers.

		
For more information on JavaCam, see the JavaCam page.

		

		

		

		

		
Dynamic HTML

		
Both Internet Explorer V4.0 and Netscape V4.0 support Dynamic HTML.  Dynamic HTML allows a JavaScript or VBScript program embedded within a page to dynamically change the content of the page.

		
For Internet Explorer users, samples of Webcam refreshes are shown here.

		
Instructions for Dynamic HTML for Netscape users will follow shortly.

		

		

		

		

		
Opening a window for continued viewing

		
A common request is to open a separate browser window for just previewing the image allowing the viewer to surf on to new web sites and pages.

		
This can be achieved easily in two steps:

		
    
			
  1. Create a Web page which will host the refreshing image.
			
  2. Create some JavaScript to open a new browser window to view the refreshing web page
		

		
Step 1 involves creating a web page which usually has just a single, refreshing image in it.

		
Step 2 is a little more complicated.  The following is a piece of JavaScript to load the refreshing page