1. A method for reducing an image representing a substantially symmetric subject, comprising the steps of: dividing the image into a first part and a second part, the second part being substantially symmetric to the first part; determining pairs of symmetrically corresponding pixels, a member of the pair in the first part having an X pixel value and a member of the pair in the second part having a Y pixel value; computing a weighted average value A of the pixel values of each one of the pairs; computing a weighted variance value B of the pixel values of each one of the pairs; representing each of the pairs with the weighted average and the weighted variance values; and generating reduced image data including at least a plurality of the pairs.