Facsimile and static presentation processing – Static presentation processing – Attribute control
Patent
1997-11-18
2000-05-16
Rogers, Scott
Facsimile and static presentation processing
Static presentation processing
Attribute control
358501, 358534, 358300, H04N 152, H04N 129, G06K 1514
Patent
active
060644958
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
This invention relates to printing systems and more particularly to halftone printing utilizing an extended color palette.
BACKGROUND OF THE INVENTION
Most printing systems use a standardized color scheme called SWOP. In this color scheme, halftone masks are developed for cyan (C), magenta (M), yellow (Y) and black (K) inks having printed solid optical densities of 1.33, 1.47, 1.0 and 1.6. This color scheme is consistent with the limitations of the standard offset lithographic printing process. Due to the fact that in this process the image is "split" several times during its transfer from printing plate to paper and due to the rheologic limitations placed on the ink by the process, higher printed solid optical densities are not achieved in the standard offset lithographic printing process.
In order to assure standardized results from different print sources, the printed solid optical densities described above have been standardized and standardized color schemes developed around these densities. Printed versions of original images having a higher color density than that available from the standard color printing schemes will have a narrower color gamut in the final printed version than in the original and the half-toning process will either truncate the higher color densities or compress the color gamut of the original into the color density range available with SWOP.
Such printing is not optimum. In order to reproduce photographs and other artwork with high fidelity, a higher printed solid optical density would be required. However, printing such higher optical densities requires additional printing steps.
Two systems utilizing additional printing steps are known. In one such system red(orange), blue (violet) and/or green inks are printed in addition to the standard CMY colors. This improves the color density possible for these colors (and mixed colors having a large proportion of the added colors) but is not effective to increase the color saturation for the entire range of colors.
A second system is based on printing the CMY colors more than once to achieve a thicker layer of ink and thus a higher color density for those portions of the image which require it. This system does give an improved color density, but requires printing each color twice. If process black is printed in addition to CMY a total of seven printing steps, one for black and two each for CMY, are required. This system is marketed by DuPont under the trade name Hypercolor.TM. Software.
SUMMARY OF THE INVENTION
The present invention is based on using a printing process and inks which enable printing higher printed solid densities with a single printing step utilizing inks or toners having a higher pigment loading. Availability of high, printed solid saturation densities allows for printing a larger color gamut.
The present invention is not limited to any particular half-toning system. While it is applicable to any halftone system since it can increase the color saturation of any system, it does reduce the color density resolution which is available. Thus it is most useful in printing (half-toning) systems which have a high dot resolution (sometimes called, pixel resolution). Dot resolution is usually described in terms of a pixel density such as 300.times.300 DPI or 800.times.800 DPI. However, the system especially useful in systems which can print pixels sizes which are greater than a minimum size but are not necessarily integral multiples of that size.
There is therefore provided, in accordance with a preferred embodiment of the invention, a method for forming halftone map comprising: printed regions of varying binary print coverage and an apparent color density for the varying coverages, for a printing process which produces printed solid color densities greater than those of the SWOP standard in a single print step; and having a given color density are replaced by binary print coverage in accordance with said half-toning scheme and said matching.
Preferably, the printing process produces a printed soli
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Indigo N.V.
Rogers Scott
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