1. An object recognition apparatus comprising: a memory configured to store at least one object-specific metric map that maps an image color space to set of metric values related to a target object; and a processor coupled with the memory and configured to operate as a recognition engine by executing the steps of: obtaining the at least one object-specific metric map; obtaining a digital representation of a scene and including image data; generating map-altered image data according to the object-specific metric map executed on the image data; deriving a metric-based descriptor set by executing an image analysis algorithm on the map-altered image data; and retrieving digital content associated with the target object as a function of the metric-based descriptor set.