Augmented Reality with HTML5
Augmented reality (AR) is the name given to a class of applications that combines the unique capabilities of mobile phones to extend users' perceptions of their environments. Layar (www.layar.com) was one of the first AR applications, and it's still one of the more creative. Augmented reality overlays the current camera preview screen with additional information—you can see examples in this YouTube video: (www.youtube.com/watch?v=A6Le50-QN3o&feature=player_embedded). Figure 1 shows what Layar looks like when the “Starbucks” layer is loaded and the camera is pointed at a mall where there is a Starbucks coffee shop.
This application makes use of a number of mobile phone features:
Compass (direction the camera is pointed).
2-D graphics (for the overlay).
Layar is a very advanced application, with many options to make it easy to use. Again, the essential nature of AR is that the user sees additional information superimposed on a camera preview.
How would you implement this kind of application using HTML5? For the sake of creating an example application, let's reduce AR to a simple case: show the current camera preview on the user's screen and superimpose the current compass direction on top of the preview. Let's also animate the compass card so it moves as the phone's camera pans around. In principle, the overlay could be anything, but a compass card is a start.
HTML5 has greatly extended the capabilities of HTML applications, but some things still are missing for this application:
You need a live camera preview on the screen, and there isn't a camera API in HTML5. Extensions to HTML5, such as WAC (Wholesale Applications Community, public.wholesaleappcommunity.com), are defining APIs for camera preview, but there are no WAC mobile phones yet.
The application will be a hybrid Dalvik/HTML5 application. The HTML5 part will run in a browser. Android applications create an Internet browser view in one of two ways:
Let's write a Dalvik application that shows the camera preview screen and overlays that with a WebView that will draw and animate the compass card. Of course, you'll also need the compass information passed from Android back to the HTML5 code, so it can animate the card properly.
Rick Rogers has been a professional embedded developer for more than 30 years. Now specializing in mobile application software, when Rick isn't writing software for a living, he's writing books and magazine articles like this one.
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