1. A method of searching for an object in an image or sequence of images by processing signals corresponding to the image or images using one or more processors, the method comprising inputting a query in the form of a two-dimensional outline; deriving, using a processor, a curvature scale space (CSS) representation of the object outline by smoothing the object outline; deriving, using a processor, at least one additional parameter reflecting the shape or mass distribution of a smoothed version of the original outline; deriving, using a processor, a query descriptor by associating the CSS representation and the additional parameter; comparing said query descriptor with each descriptor for stored objects using a matching procedure using the CSS values and the additional parameters to derive, using a processor, a similarity measure; and selecting and displaying at least one result corresponding to an image containing an object for which the comparison indicates a degree of similarity between the query and said object.