Model based error diffusion with correction propagation

Claim 2

An error diffusion with correction propagation method for printing grey scale or color images comprising the steps of: defining a matrix D of printing decisions and a matrix V of actual areas in each pixel covered by a printing action; storing data of a continuous tone source image I in an image Random Access Memory (RAM), an output from the image RAM being an input signal u for each pixel (i,j) of I, where i and j refer respectively to horizontal and vertical coordinates of the pixel being treated; adding a weighted error signal y to the input signal u to generate an output signal x; comparing the output signal x to a threshold t and generating a printer decision signal based on the threshold t; storing a predetermined number of past printing decision signals in the matrix D; generating printed values in the matrix V given by the stored past printing decision signals; generating a threshold t from the matrix V as t=V(i,j); calculating current states in a matrix S using the output signal x and the matrix V, updating states in pixels N(i,j) and propagating the states to pixels in M(i,j); updating past errors in E(i,j) using the propagated states from the matrix S and the matrix V; calculating the weighted error signal y as a weighted sum of the errors E(i,j); and outputting printer decision signals to a printer to print a grey scale or color image.

Claim 3

The error diffusion method for printing grey scale or color images recited in claim 1, wherein the step of calculating the weighted error signal y is performed by calculating ##EQU4##

Claim 4

The error diffusion method for printing grey scale or color images recited in claim 1, further comprising the step of scanning an image to generate a digitized version of the image for storing in the image RAM.

Claim 5

The error diffusion method for printing grey scale or color images recited in claim 3, further comprising the step of converting a scanned color image from red, green, blue to cyan, yellow, magenta, black (RGB-CYMK) for printing a color image.

Claim 6

A halftoning printer apparatus incorporating error diffusion with correction propagation for printing grey scale or color images comprising: an image Random Access Memory (RAM) for storing data of a continuous tone source image I, an output from the image RAM being an input signal u for each pixel (i,j) of I, where i and j refer respectively to horizontal and vertical coordinates of the pixel being treated; an adder for adding a weighted error signal y to the input signal u to generate an output signal x; a comparator connected to the adder for comparing the output signal x to a threshold t and generating a printer decision signal based on the threshold t, the comparator outputting printer decision signals to a printer to print a grey scale or color image; a matrix D of printing decisions and a matrix V of actual areas in each pixel covered by a printing action, a predetermined number of past printing decision signals being stored in the matrix D and printed values being generated and stored in the matrix V given by the stored past printing decision signals; a threshold generator connected to the matrix V for generating a threshold t from the matrix V as t=V(i,j); a calculator for calculating current states in a matrix S using the output signal x and the matrix V, updating states in pixels N(i,j) and propagating the states to pixels in M(i,j); an error calculator for updating past errors in E(i,j) using the propagated states from the matrix S and the matrix V; and a weighted error calculator for calculating the weighted error signal y as a weighted sum of the errors E(i,j).

Claim 7

A halftoning printer apparatus incorporating error diffusion with correction propagation for printing grey scale or color images comprising: an image Random Access Memory (RAM) for storing data of a continuous tone source image I, an output from the image RAM being an input signal u for each pixel (i,j) of I, where i and j refer respectively to horizontal and vertical coordinates of the pixel being treated; an adder for adding a weighted error signal y to the input signal u to generate an output signal x; a comparator connected to the adder for comparing the output signal x to a threshold t and generating a printer decision signal based on the threshold t, the comparator outputting printer decision signals to a printer to print a grey scale or color image; a matrix D of printing decisions and a matrix V of actual areas in each pixel covered by a printing action, a predetermined number of past printing decision signals being stored in the matrix D and printed values being generated and stored in the matrix V given by the stored past printing decision signals; a threshold generator connected to the matrix V for generating a threshold t from the matrix V as t=V(i,j); a calculator for calculating current states in a matrix S using the output signal x and the matrix V, updating states in pixels N(i,j) and propagating the states to pixels in M(i,j); an error calculator for updating past errors in E(i,j) using the propagated states from the matrix S and the matrix V; and a weighted error calculator for calculating the weighted error signal y as a weighted sum of the errors E(i,j).

Claim 8

The halftoning printer apparatus as recited in claim 5, wherein the weighted error calculator calculates the signal y as ##EQU5##

Claim 9

The halftoning printer apparatus as recited in claim 5, further comprising a scanner for scanning an image to generate a digitized version of the image for storing in the image RAM.

Claim 10

The halftoning printer apparatus as recited in claim 7, further comprising a color converter connected to the scanner for converting a scanned color image from red, green, blue to cyan, yellow, magenta, black (RGB-CYMK) for printing a color image.