A method for analyzing an image composed of pixels by estimating a continuous function of a selected pixel attribute, the continuous function being centered on a selected pixel position, the method comprising: determining a series of nested sets of pixels, each set being centered on a common pixel; estimating a discrete weighting for each set of pixels in accordance with the continuous function; mapping the sets of pixels onto pixels of the image with the common pixel mapped on to the selected pixel position; for each set of pixels, forming a combined value in dependence on the values of the selected pixel attribute for the pixels of the set in the image; and estimating the function as a sum of the combined values for each set weighted by the respective discrete weighting.