Patent ID: 7365881

Claim:
A method for converting an original halftone bitmap image to a color converted halftone bitmap image by morphological filtering of the original image to compensate for tone and color reproduction characteristics comprising: providing an original halftone bitmap image; providing a set of one-dimensional asymmetrical morphological filters that have a property (a) that their structuring elements are not even functions in their respective one-dimensional directions, and (b) that when they are applied recursively in order, the features in the halftone bitmap image are dilated or eroded by varying amounts by extending or reducing the edges at least in one direction, and then in another direction; segmenting the original halftone bitmap image into blocks and for each block: (a) applying said set of morphological filters to said original halftone bitmap image to produce a set of modified halftone bitmap images; (b) estimating a percent dot area of the original halftone bitmap image and for each of the set of modified halftone bitmap images; (c) applying a predetermined dot-gain to the percent dot area of the original halftone bitmap image to produce a modified percent dot area; and (d) from the set of modified halftone bitmap images, selecting a modified halftone bitmap image whose percent dot area is closest to the modified percent dot area to produce a block of the color corrected halftone bitmap image; and replacing said original halftone bitmap image with the block of the color corrected halftone bitmap image.