1. A method to identify regions, the method comprising: receiving an image of a scene of real world; creating a plurality of sets of positions automatically, by at least performing comparisons using multiple pluralities of pixels hereinafter compared pixels that are located in the image at corresponding positions comprised in the plurality of sets of positions; wherein a first set in the plurality of sets of positions is created without using in any comparison, a plurality of pixels hereinafter skipped pixels that are located in the image at additional positions comprised in the first set; wherein a first region identified by the first set is contiguous in the image, the first region comprising the compared pixels and the skipped pixels identified respectively by the corresponding positions and the additional positions; wherein a second region is contiguous in the image, the second region being identified by positions in a second set, in the plurality of sets of positions created by the creating; checking automatically, whether a test is satisfied by a first attribute of the first region and a second attribute of the second region; preparing automatically, a merged set comprising the positions in the first set and the positions in the second set, based on at least an outcome of said test; and storing automatically, in one or more memories, the merged set; wherein the receiving, the creating, the checking, the preparing and the storing are performed by one or more processors coupled to the one or more memories.