Color halftoning by indexing the visual-optimized dot profiles

A new haiftoning method for color image is proposed. The proposed algorithm is very simple to implement the halftoning in hardware and software, which indexes the image pixel values to a binary database as proposed by Sullivan et a!. The database is a set of dot profiles representing the corresponding gray levels. The dot profiles are sequentially generated from a visual-optimized seed pattern which is well-distributed by contrast sensitivity function (CSF), in order that the dot profiles have the visual-optimality as well as correlation between dot profiles ofall gray levels. Circular convolution technique is used for generating the dot profiles so that the periodic blocking artifacts can be reduced. The proposed color halftoning method uses one database which is shared for all color components and can be directly used for monochrome haiftoning, but each color component has different indexing scheme with a circularly shifted indexing to reduce the correlation between dot profiles of color components. The simple structure and small memory requirement of the proposed halftoning method make the processing time fast. The halftone image quality ofthe proposed method is better than that of ordered dither.