1. A non-transitory machine readable medium storing instructions which when executed by a processing system cause the processing system to perform operations, the operations comprising: storing a setup metadata entry comprising dimensions of image data in a pixel-independent coordinate system and comprising an indication of a total number of detected objects; storing a detected object metadata entry for each detected object, each detected object metadata entry comprising information that provides a location and dimensions of a perimeter around a detected object, wherein the information provides the location and dimensions of the perimeter in the pixel-independent coordinate system.