Apparatus and method for generating multi-level output values for pixels in a halftone cell

Abstract

Apparatus and a method for generating a multi-level halftone image (104) from a digitally sampled continuous tone image (101). The apparatus includes a control circuit (140), a preference matrix (150) having as its matrix elements addresses of a plurality of look-up tables (160) and a plurality of look-up tables (160) in the form of a look-up table stack (155). Generally, the control circuit (140) instructs the preference matrix (150) to select a look-up table (160) from the look-up table stack (155) in a pre-defined manner. The selected table (160) is used to convert an intensity value (102) into a multi-level pixel value (106) in the halftone image (104). To accomplish the conversion, each look-up table (160) contains a quantized one-dimensional transfer function (165') having as an input the magnitude of the intensity value (102). The magnitude is mapped into an output level by the transfer function as one of a plurality of available levels. The output level is assigned a pixel location in a halftone cell (103). The look-up table selection is repeated for each element of the preference matrix (150) and the magnitude of each intensity value (102) is mapped into the halftone cell (103) to generate a multi-level halftone image (104).

Dependencies are inferred from the claim text.