[Patrickwhite]

The class ParticleAnalysisReport has several public fields that give you useful information about particles. A "particle", often referred to in image processing as a "blob", is a group of continuous pixels.

A single report details the information about one particle - where it's located on the screen, its bounding box (the box in which all the pixels of the particle are contained), its size, and a few other useful things. The particleArea field, for example, represents the number of pixels in the image.

Greg's whitepaper details a simple algorithm for finding rectangles: Threshold image -> apply "convex hull" operation -> find the best "rectangle scores".

The rectangle score is the percentage of the area of the bounding box that is covered by pixels. The "convex hull" operation is a bit more complex to access - if you want to get at it see JewishDan's thread about accessing the C/C++ imaging functions in Java. But the particle properties alone should be enough to at least get you started.