1. A method of processing image data containing pixel values for pixels, said pixels being oriented in said image data in horizontal rows and vertical columns, said method comprising the steps of: examining a focus pixel in said image data; performing calculations on pixel values of a subset of pixels in horizontal rows immediately above and below the row of said focus pixel to form a first result, said calculations to detect whether the image region contains an edge; performing calculations on pixel values of a subset of pixels in vertical columns immediately to the left and to the right of the column of said focus pixel to form a second result, said calculations to detect whether the image region contains an edge.