Facsimile and static presentation processing – Natural color facsimile – Color correction
Patent
1996-09-04
1998-11-10
Coles, Edward L.
Facsimile and static presentation processing
Natural color facsimile
Color correction
358515, 358518, 382167, G03F 308
Patent
active
058352449
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention is in the field of electronic reproduction technology and is directed to a method and to an apparatus for the conversion of color values, for the purpose of adaptation to a printing process given devices and systems for image processing.
Reproduction technology is concerned with methods for reproducing image originals in printing, wherein a copy master is produced from an original as a basis for a printing form. The reproduction of the original occurs in a printing press with the printing form.
The manufacture of the copy master generally occurs in the steps of image input, input processing and image output.
In the image input with, for example, a color image scanner (scanner) as input device, three primary color value signals R, G and B are acquired by trichromatic as well as pixel-by-pixel and line-by-line optoelectronic scanning of a color original to be reproduced, whereby the individual color value triads represent the color constituents "Red" (R), "Green" (G) and "Blue" (B) of the pixels scanned in the color original. The analog color value signals are converted into digital color values and are stored for the subsequent image processing.
In the image processing, the color values R, G and B are first converted into color separation values C, M, Y and K by a basic color correction according to the laws of subtractive color mixing, these color separation values being a measure for the dosage or, respectively, for the raster point sizes of the inks "Cyan" (C), "Magenta" (M), "Yellow" (Y) and "Black" (K) employed in the later printing process. Beyond this, further color corrections are implemented in the image processing with the object of improving the image reproduction, compensating deficiencies or undertaking editorial changes.
After the image processing, the image output occurs with a suitable output device, for example with a color separation exposer (recorder) for the rastered recording of the color separations "cyan", "magenta", "yellow" and "black" on a film.
The demand is often raised to be able to connect various input and output devices to a color image processing system. For that purpose, the introduction of a defined standard for the color values at the interface between image input and color image processing and at the interface between color image processing and image output is of great advantage. For that purpose, the color values R, G and B generated in the input device must be transformed onto the respective, internal standard of the color image processing system, for example into the color values L*, a* and b* of the CIELAB color space, must be processed and the standardized and corrected values L*, a* and b* must then be converted into the color separation values C, M, Y and K for the exposure of the color separations in the form of a conversion table, referred to below as a printing table.
The literature, for example, the periodical "Der Druckspiegel", No. 6, 1991, pp. 580-592, the article "Farbe in der Bildverarbeitung" already discloses that the color values of a device-dependent input color space acquired in a color image scanner be transformed for a universal color presentation into color values of a device-independent communication color space on the basis of a color space transformation, that the corresponding corrections be undertaken on the basis of the transformed color values, and that the corrected color values then be converted by a further color transformation into the corresponding process color values of a device-dependent output color space.
EP-A-0 528 094 already discloses a method for calculating a printing table. Therein, a measuring of the corresponding color values as well as a subsequent interpolation occur for calculating intermediate values. As a result of the expense incurred, relatively few supporting values are identified and interpolation is carried out between these supporting values. Due to the small number of supporting values, only a limited precision can be achieved. A further possibility for calculating a p
REFERENCES:
patent: 4959669 (1990-09-01), Haneda et al.
patent: 5196927 (1993-03-01), Warner
patent: 5333069 (1994-07-01), Spence
patent: 5416613 (1995-05-01), Rolleston et al.
patent: 5420704 (1995-05-01), Winkelman
patent: 5481380 (1996-01-01), Bestmann
patent: 5493321 (1996-02-01), Zwadlo
patent: 5668890 (1997-09-01), Winkelman
Coles Edward L.
Linotype-Hell AG
Nguyen Madeleine A. V.
LandOfFree
Method and apparatus for the conversion of color values does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method and apparatus for the conversion of color values, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method and apparatus for the conversion of color values will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1522561