how to find a face in an image code
Look in these papers:
VIOLA, P., AND JONES, M. Rapid object detection using a boosted cascade of simple features. In Proceedings IEEE Conf. on Computer Vision and Pattern Recognition (2001).
VIOLA, P., JONES, M. J., AND SNOW, D. Detecting pedestrians using patterns of motion and appearance. In iccv03 (Nice, France, 2003), pp. 734–741.
I want to build it too (in Matlab first). I've just read them but there are some inconsistencies, especially in the sum-of-filters construction. Hope we could help each other.