A method determines a contribution of an object to an intensity value of a current pixel that is partially covered by the object by calculating an entry location and exit location for an edge of the object in the current pixel, the entry and exit locations being located on boundaries of the current pixel with different orientations. The method determines an intensity value for at least one neighboring pixel located adjacent to the current pixel, the neighboring pixel being selected based on the calculated entry and exit locations, and then determines an intensity value of the current pixel using the determined intensity value of the at least one neighboring pixel as a contribution of the object at the current pixel.