Crosfield Electronics Limited

Samuel E Darby

Clive L Mayne

George Charles Manley

Brent A Hayhoe

Digital signals are generated for each pixel of an image to be reproduced, corresponding to the values of color components in each pixel. The respective color component values of each pixel are applied to a set of look-up tables (30) so loaded that they recognize whether the color component values of a pixel fall within a color range(s) for which a processing operation is to be carried out. The look-up tables provide an output signal representing one of a number of possible processing operations for that pixel, in the form of an operation number. The operation number signal is applied through a processor (32) to an operation select table (36) which converts the operation number into a specific processing operation for each color component. The processing operations may be retouching, image retention (no change), replacement by a tint value, or dropout. They are carried out by components (44, 42, 38 and 40) under the control of the operation select table, and the resulting pixel values are transferred to an output buffer (24). The look-up tables may define the color ranges within which processing operations are required in terms of a range of a single color component or coinciding ranges of 2, 3 or 4 color components.

Pixel color modification using look-up tables in image reproduction

A method and apparatus for modifying an image represented by digital data defining the content of one or more pluralities of cells constituting one or more color separations is described. The digital data indicates for each cell whether the respective color is 'present' or 'absent'. The apparatus comprises scanning means (15,16) for electronically scanning along a plurality of scan lines with a mask of preselected dimensions; the respective plurality of digital data corresponding to a region including a boundary for one or more of the color separations. Programmable logic determines at each position of the mask whether the portion of the color separation within the mask includes at least one cell the content of which indicates color 'present'; and modifies the digital data at another, predetermined position within the mask to change the content of the respective cell or cells of the color separation to represent color 'present' or color 'absent' when color 'present' is detected within the mask. The boundary is thus 'gripped' either positively or negatively.

Image modification

Method and apparatus for generating a half-tone dot representation of an original image which has been previously generated as one or more color separations each comprising a plurality of cells (12), each cell being digitally encoded in accordance with the color density at that point is described. The apparatus comprises a record medium support (8); a plurality of scanning beam generators arranged side by side, the scanning beams (B1-6) and the record medium support (8) being relatively movable. First control means controls the scanning beams during relative movement between the scanning beams and the record medium support (8) in response to the digital information and half-tone dot information to generate a plurality of half-tone dots (14) at a first rate, each dot corresponding to one or more of the plurality of cells (12). Storage means (23) for storing additional control information; and second control (24) means for determining the position of the scanning beams relatively to the record medium, determining whether that position corresponds to part of a boundary of an image poriton, and, if it does, for at least one color separation, for each cell at the boundary of an image portion modifying the plurality of scanning beams in response to the additional control information:

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Harrow, United Kingdom

Samuel E Darby