Graphics Reference
In-Depth Information
Robustness
. We are very happy with our Android app and its performance. We
played with it a lot to ensure that it runs robustly (and it does!). For example, it does
not require special illumination—it works well in a variety of lighting conditions as
long as there are no sharp shadows on the board.
Real-time operation
. Although it was written in Java under Android and runs on
an ARM (a small processor in a smartphone), our app runs at about five frames per
second. This is fast enough to ensure smooth interaction with the user and so we can
call it a “real-time” operation.
Limitations
. We tested our app in many situations and found that the major
drawbacks are:
The phone must be held carefully to capture only the tic-tac-toe board and nothing
else
The phone must be held at a distance of about 10-30 cm from the tic-tac-toe board
because the app does not have auto-focus. This distance dictates that the size of
the board needs to be about 10 cm on a side
The lines must be drawn almost entirely straight, otherwise the cells may be incor-
rectly detected
The X's and O's must be fairly symmetric because the algorithm relies on the
centroids of these symbols
The app works well despite global illumination changes (we tried it in low and high
room light) but if there are local illumination changes (such as sharp shadows),
the system may give incorrect results.
Acknowledgments
Many thanks to Drs. Darnell Moore and Rajesh Narasimha for their valuable
comments during our school science fair, to Stanford University for open-sourcing their EE368
Viewfinder Android app and to Ranjith Parakkal, Takashi Nishizaki, and Dossan George, all from
Uncanny Vision, for their generous support with Neon evaluation and their UncannyCV library.
References
1. de Praves D, Terni Lapilli.
http://www.latinpraves.blogspot.com
2. Dewdney K (1993) A Tinkertoy computer that plays tic-tac-toe.
http://www.rci.rutgers.edu/
3. Sudoku Grab.
http://sudokugrab.blogspot.com/2009/07/how-does-it-all-work.html
4. Eyes On Road.
http://www.eyesonroad.co.il
5. Google Project Glass.
http://www.google.com/glass
6. Quiroga RQ, Fried I, Koch C (2013) Brain cells for grandmother. Sci Am 308(2):30-35
7. Park D (1997) The fire within the eye. Princeton University Press, Princeton
8. Rock I (1995) Perception. Scientific American Library, New York
9. Zeki S (1992) The Visual Image in Mind and Brain. In: Special issue of scientific American
on mind and brain
10. Forsyth D, Ponce J (2011) Computer vision: the modern approach, 2nd edn. Prentice Hall,
New Jersey
11. Android Developers.
http://developer.android.com
12. Stanford EE368.
http://www.stanford.edu/class/ee368
13. Tic-Tac-Tandroid on YouTube.
http://www.youtube.com/watch?v=TCoBJy_W1ms
