A method for scanning for borders in an image represented by pixels, the method including a first operation comprising: estimating an attribute for each of a first set of two adjacent pixel positions in the image; assessing whether a predetermined binary condition differs in respect of the two pixel positions, and if so determining that a border is present in the part of the image represented by pixels at those positions; and if a border is determined to be present in that part of the image, estimating the direction of the border as being perpendicular to a line joining the positions of the two pixels; and initiating tracing the border in that direction.