1. A method of detecting an object in an image at a client device, comprising the steps of: receiving from a server a two dimensional image of a scene, the scene being captured by a camera and the image comprising an object located within the scene, receiving from the server position data, the position data being indicative of the position of the object within the image; receiving from the server an outline representation of the object at that position, the outline representation defining for pixel positions in a segment of the image at that position whether the pixel position represents the object; and on the basis of said outline, detecting the object in the image.