[plt-scheme] Writing a game and have questions

I am writing a game using DrScheme (actually am implementing this existing game http://www.bubblebox.com/play/puzzle/539.htm) and have some questions that I ran into along the way. 

I draw a tiled array of hexagons on a canvas using paths. Now I would like to detect which hexagon is beeing clicked on. One way of implementing this would be to render the hexagons to an offscreen buffer on startup - where each hexagon is drawn using a unique color. When the user clicks on screen, i fetch the color from the offscreen buffer and figure out the hexagon being clicked on. For this I have two questions 

1) Is it possible to draw a canvas to an offscreen buffer ?
2) Is it possible to fetch pixel values from a canvas. 

Feel free to suggest any alternative approaches to solving the same problem. 

Thanks,
Deepankar
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