html5 canvas question

I have been experimenting with html5 quite a bit lately to see what I can build. In doing so I have looked at alot of examples especially from http://www.beautyoftheweb.com. In alot of the examples it seems like people that have created these applications can keep track of the elements on the canvas. However, I cannot seem to figure out how to keep a reference to an element on the canvas. Is it possible or are they doi开发者_JS百科ng something else to find the element. For example if I take an image and put it on the canvas I have no reference to that element except by doing canvas.getImageData(). If it is possible to keep a reference to an element it would be great if someone could give me an example of how to do so or a link to a tutorial would be great. If its not possible how are they doing it?

thanks in advance for any help.

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Everyone has to write their own code to remember whats drawn and how to interact with it. (Or else use a libarary).

I've actually written two tutorials on precisely this subject. They should be enough to get your started:

Making and Moving Selectable Shapes on an HTML5 Canvas: A Simple Example

Selectable Shapes Part 2: Resizable, Movable Shapes on HTML5 Canvas