1. A computing device for tracking an object in an image stream, said computing device comprising: a memory; and a controller, wherein said memory has stored therein instructions that, when loaded and executed on a processor, causes the controller to: receive an image stream comprising at least a first and a previous image of an object to be tracked; determine at least one contour line in at least said first image, wherein said contour line comprises a plurality of points; determine and assign at least one descriptor to each point; filter out points based on the descriptors; determine relative distances between each point in said first picture with each point in said previous picture, which points have not been filtered out; determine a maximum occurrence for the relative distances, determine a mean position of each point pair; determine a relative distance for each point pair and determine a slope of a corresponding linear fitting of said relative distances versus said mean positions, and determine a movement in a direction parallel with a line of sight based on the slope, wherein the maximum occurrence corresponds to a movement of said object to be tracked.