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Reverse Green Screen: Experiment

November 14, 2009

Time to start expanding the possibilities of actionscript and flash! I’ve already written up a list of ideas to try out. My goal will be to try them out to see how feasible  they are (though one limiting factor might be my own programming capabilities).

One of the first experiments on the list is “The Reverse Green Screen”. As the name should imply the idea is very similar to a traditional green screen: remove the background, keep the foreground image. The reverse green screen, however, uses a colored foreground, instead of a colored background. This would be done by using a tinted light source directed towards the foreground subject. The idea is that in a room already lit with white light, a smaller tinted light source facing the subject would only cast a tinted color on the foreground subject while the tint would become muted by the white light as the distance from the colored light source becomes farther. Using, actionscript, I believe I can select for a certain color range, thereby selecting the foreground and omitting the background. I think it should also be possible to counteract the appearance of the tint of the video image by adjusting the color of the outputted color image.

The reasoning: Why would I want to try this? As a simple, makeshift solution that may help with a more complex problem. Using a single webcam with Adobe Flash, we may not have the capability to perform some more complex forms of computer vision. One issue in this setup is differentiation of the subject from background interference. My proposed solution uses the factor of proximity in a single camera system and may be combined with other object detection methods (assuming this experiment is a success). Even if the experiment is not, at a least a record will be made that this idea has been attempted. In addition, I’d like to note that a conventional and successful way of using proximity for motion capture has been the use of infrared cameras to detect sources that are closer.

The problems: Some possible problems I think I forsee include the interaction of tint with dark colors. Dark colors are known to absorb light and may not as readily display the tint. Another problem will be to see the spectrum of colours created by casting a colored light on various colored surfaces (How will I select for them all? What color of light should I use?  How bright a light source is needed? Is this idea crazy!?!?! We’ll never know unless I try).

Comments, Question, Hints, tips and links are all welcome and appreciated.

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