1. A method of representing a 2-dimensional image I(x, y) comprising: deriving at least two 1-dimensional representation of the image by projecting the image onto at least perpendicular X and Y axes aligned with the edges of the images, wherein projection onto an axis A involves, for each position a on axis A, summing image values for pixels along a line perpendicular to axis A at position a, and wherein projection onto X and Y axes is computed as XProjection ⁡ ( x ) = ∑ y ⁢ I ⁡ ( x , y ) , ⁢ YProjection ⁡ ( y ) = ∑ x ⁢ I ⁡ ( x , y ) applying a windowing operator to said at least two 1-dimensional representations to reduce artifacts caused by signal boundaries, using a predetermined window function with constant parameters and a size dependent only on a length of a 1-dimensional representation; and applying a Fourier transform to each windowed 1-dimensional representation.