Method of and apparatus for generating halftone image with compensation for different dot gain characteristics

DETAILED DESCRIPTION An object of the present invention is accordingly to compensate dot gain characteristics of different dots types.
The present invention is directed to a method of generating a halftone image from an image signal representing an original image.
The method comprises the steps of: (a) dividing the original image into a plurality of image areas and assigning one of a plurality of dot types to each of the plurality of image areas, the plurality of dot types having a difference in dot gain characteristics between each other; (b) providing an image signal and a plurality of dot pattern signals, the plurality of dot pattern signals representing threshold values adaptable to generate respective dots of the plurality of dot types; (c) executing tone correction on at least either of the image signal and the plurality of dot pattern signals to compensate for the difference in dot gain characteristics between the plurality of dot types; and (d) comparing the image signal with one of the plurality of dot pattern signals after the tone correction in each of the plurality of image areas, to thereby generate an image recording signal representing a halftone image in which each of the plurality of image areas is reproduced with one of the plurality of dot types assigned to the each of the plurality of image areas.
Accordingly, the original image is reproduced with compensated dot gain characteristics of each dot type even when different types of dots are applied to one image.
In a preferred embodiment of the present invention, the step (c) comprises the step of: correcting the image signal to compensate for the difference in the dot gain characteristics.
Alternatively, the step (c) comprises the step of: correcting the plurality of dot pattern signals to compensate for the difference in the dot gain characteristics.
The plurality of dot types comprises a high resolution dot having a relatively high resolving power, and a low resolution dot having a relatively low resolving power.
The high resolution dot includes a Frequency Modulation dot whose frequency of appearance is varied with image density