Loads and scans images for TopCodes. The algorithm does a single sweep of an image (scanning
one horizontal line at a time) looking for TopCode bullseye patterns. If the pattern matches
and the black and white regions meet certain ratio constraints, then the pixel is tested as the
center of a candidate TopCode.
TopCodes (Tangible Object Placement Codes) are black-and-white circular fiducials designed to
be recognized quickly by low-resolution digital cameras with poor optics. The TopCode symmbol
format is based on the open SpotCode format: