direction of dither is independent of the other rows or columns allowing all rows or columns to be corrected simultaneously in the first embodiment no corrections are made on a pixel until corrections have been calculated for the entire row in the second embodiment however the pixel corrections are made 34 on the fly 34 allowing the corrections to always be made with the most up to date information on every pixel in accordance with the first embodiment with reference also to fig3 pixels are read from the image buffers 3 5 and are corrected using the correction factors from the correction buffer 9 the difference between these pixels is computed and divided by two to form a correction update this correction update is then subtracted from the correction factor corresponding to the left hand pixel and added to the correction factor corresponding to the right hand pixel these new values are then stored in latches 15 and 17 index 34 j 34 then increments and the entire process repeats after the entire row has been corrected a clock strobes the latches 15 17 and the newly formed correction factors are used to update the correction buffer 9 in accordance with the second embodiment the process is identical to that of the first embodiment except for the clock speed in this case a high speed clock updates the correction factors on the current pixel pair before incrementing index 34 j 34 as a result when the difference between pixel i j and pixel i j 1 is formed it is formed with a comprehension of the correction already made on pixel i j the correction on pixel i j likewise.