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