error row memory and the error values in the row behind the next row equal to 0 before the current row is processed writing the final accumulated error value on a certain position of the row next to the current row is implemented after the error rows corresponding to the following two pixels are read out in this course the read error rows have three original accumulated error values therefore only three original values of the error rows in the next row are needed to be stored in the error buffer register file in the present embodiment as shown in fig6 the error buffer register file is able to buffer all of the error distribution values of the adjacent five pixels and the three original values of the error rows in the next row wherein p 5 is set as the current operating pixel p i d j i j 1 5 respectively denote all of the error values of p 5 and its four preceding adjacent pixels in the same row and p i l 1 i 3 4 5 respectively denote the original accumulated error values of the row following the row at which the read position p i locates in the.