ERROR DIFFUSION METHOD AND APPARATUS

The invention relates to a method of diffusing error caused by quantizing each pixel within an image formed of a plurality of pixels, each pixel representing a greyscale value of the image at a location (n, l) within the image, and having an original greyscale value associated therewith. The method includes the steps of adding to the original greyscale value of a pixel having a position (n, l) within the image a first error term resulting from quantization of previously processed pixels to derive a modified greyscale value, comparing the modified greyscale value of the pixel with a threshold to select an output value representing the pixel, calculating a second error term having a value that is the difference between the output value and the modified greyscale value, and distributing the second error term to a preselected plurality of neighboring pixels at positions (n+1, l), (n−1, l+1), (n, l+1), (n+1, l+1) using a linear phase filter algorithm having a set of distribution coefficients with a sum less than one, wherein one coefficient within the set of coefficients is combined with the second error term for each pixel position. The method also includes these steps being repeated for each pixel within the image. In another embodiment, the portion of the second error term distributed to the pixel at position (n+1, l+1) equals the portion of the second error term distributed to the pixel at position (n−1, l+1).