MEMORY EFFICIENT HIERARCHICAL ERROR DIFFUSION WITH COLOR CONSISTENCY CONSTRAINTS

摘要

A halftoning process for printing digital images includes: receiving CMYK input pixel data that define an input pixel of an input digital image in terms of continuous tone input data values for cyan, magenta, yellow, and black colors, wherein I(C), I(M), I(Y), I(K) respectively correspond to the continuous tone input data value for the cyan, magenta, yellow, and black colors; converting the CMYK input pixel data to modified CMYKRGB* pixel data that define the input pixel in terms of error-adjusted continuous tone data values for the cyan, magenta, yellow, and black colors, and also in terms of red, green and blue colors, wherein I*(C), I*(M), I*(Y), I*(K), I*(R), I*(G), I*(B) respectively correspond to the error-adjusted converted continuous tone input data values for the cyan, magenta, yellow, black, red, green, blue colors; quantizing the modified CMYKRGB* pixel data to derive intermediate output CMYKRGB pixel data in which the cyan, magenta, yellow, black, red, green, and blue colors are each defined by either a first quantized value that represents no color or a second quantized pixel value that represents full color, wherein O′(C), O′(M), O′(Y), O′(K), O′(R), O′(G), O′(B) respectively define said intermediate output pixel data for the cyan, magenta, yellow, black, red, green, and blue colors, and wherein the intermediate output CMYKRGB pixel data define an output pixel that corresponds to the input pixel; converting the intermediate output CMYKRGB pixel data to CMYK output data in which the output pixel is defined in terms of CMYK output values O(C), O(M), O(Y), O(K) respectively for the cyan, magenta, yellow, and black colors, wherein each of the CMYK output values is defined by either a first output value representing no color or a second output value representing full color.