1. A method for constructing a composite image of at least a portion of an object based on a plurality of source images, each of the plurality of source images including at least that portion of the object, each of the plurality of source images corresponding to a different focal plane with respect to the object, the method comprising: performing a first type of analysis of the source images, at at least some of a plurality of spatial locations in the source images, to determine a first set of pixels of the composite image corresponding to at least one of edges and boundaries in the composite image; performing a second type of analysis of the source images, at at least some of the plurality of spatial locations in the source images, to determine a second set of pixels of the composite image corresponding to surfaces in the composite image.