Printing – Multicolor
Reexamination Certificate
2000-09-18
2001-12-04
Hilten, John S. (Department: 2854)
Printing
Multicolor
C101S484000, C400S074000
Reexamination Certificate
active
06324975
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a color correcting method preferably applicable to a printing proof generating system for generating a color printing proof (also referred to as “printing proof” or “proof”) which comprises a proof color image on a proof sheet, with a printing proofer (also referred to as “proofer”) such as a color printer or the like before a color print is produced on a print sheet by a color printing press such as a rotary press or the like.
BACKGROUND ART
Heretofore, before a color print which comprises a color image as a halftone dot image formed on a print sheet as a final product is produced by a color printing press, it is customary to generate a proof for proofing colors with a printing proofer such as a color printer or the like as an image output device.
The printing proofer is used because it can produce a hardcopy comprising a color image on a proof sheet (recording sheet), i.e., a proof, easily a plurality of times in a short period of time without the need for plate films and presensitized plates (PS plates) as is the case with printing presses.
In order to form a proof color image on a proof sheet, image data depending on a device [printing mediums (inks, printing presses, sheets, etc.), photos, image sensors, CRTs, LEDs, etc.], e.g., CMYK (cyan, magenta, yellow, black) image data, is converted into colorimetric data as device-independent image data, e.g., Lab image data or XYZ image data mathematically compatible therewith, by a standard printing profile (four-dimensional look-up table) given by a manufacturer or the like. Thereafter, the colorimetric data is converted into device-dependent image data for a color printer, e.g., RGB (red, green blue) image data, by a printing proofer profile (hereinafter referred to as “proofer profile”), e.g., a printer profile (three-dimensional look-up table). Using the device-dependent image data, a proof with a color image formed on a proof sheet is generated by a color printer (also referred to as “proofing printer”).
The colors of a print to be produced by the printing press can be simulated by the proof generated by the color printer, so that the colors can be confirmed before they are actually printed.
Actually, the color reproduction range of the printing press and the color reproduction range of the printing proofer are different from each other. Therefore, a range that cannot be reproduced by the printing proofer is achieved by linking the printing profile and the proofer profile according to gamut mapping (color reproduction range mapping).
When a proof whose colors correspond to those of a print as a target is outputted from the printing proofer using the profiles thus linked, if the proof does not have sufficient color agreement, then the device-dependent image data CMYK are subjected to fine gradation adjustments (tone curve adjustments) prior to using the linked profiles.
However, such fine gradation adjustments are tedious and time-consuming because it is not clear as to what and how color shifts have to be corrected, and are also problematic in that some color shifts cannot be corrected by fine gradation adjustments.
The present invention has been made in view of the above drawbacks. It is an object of the present invention to provide a color correcting method which is capable of equalizing the colors of a proof produced by a proofer with the colors of a print as a target easily, reliably, and more accurately.
DISCLOSURE OF THE INVENTION
According to the present invention, there is provided a color correcting method for converting input image data depending on printing conditions into colorimetric data with a printing profile, thereafter converting the colorimetric data into image data depending on proofer conditions with a proofer profile, and outputting a proof from a proofer based on the image data to simulate color reproduction accuracy, comprising the steps of:
converting image data depending on the printing conditions to output a printing color chart colorimetrically measured when the printing profile is produced, into image data depending on the proofer conditions via the printing profile and the proofer profile;
supplying the image data to the proofer to output a proof color chart from the proofer;
colorimetrically measuring the proof color chart to generate a printing color reproduction profile to be simulated by the proofer;
determining differences between the printing color reproduction profile and the printing profile with respect to an entire color space of the input image data depending on the printing conditions; and
correcting the colorimetric data with the determined differences.
With the arrangement of the present invention, a color chart for generating a printing profile is outputted as a proof from a printing proofer. As with an original printing profile, the proof is colorimetrically measured to determine a conversion relationship between image data depending on proof conditions and colorimetric data, i.e., a printing profile (printing color reproduction profile). Differences between the printing profile and the printing color reproduction profile determined from the proof are determined with respect to an entire color space of input image data depending on printing conditions, and used to correct colorimetric data outputted from the printing profile.
By thus correcting the colorimetric data, adjustments of tone curves of respective colors are not required, and the colors of the proof can easily and reliably be equalized with the colors of a print.
In the step of correcting the colorimetric data with the determined differences, the determined differences may be added to the original printing file (actually, the determined differences subtracted from the original printing file as their sign is inverted), producing a corrected printing profile. By using the corrected printing profile, a memory or the like as a storage means is not excessively used, and adjustments of tone curves of respective colors are not required, with the result that the colors of the proof can easily and reliably be equalized with the colors of a print.
The determined differences may be multiplied by a weighting coefficient depending on values of the input image data depending on the printing conditions in the entire color space, and the differences multiplied by the weighting coefficient may be added to the printing profile to correct the printing profile. The colors of the proof can more accurately be equalized with the colors of a print.
Rather than determining the differences between the printing color reproduction profile and the printing profile with respect to the entire color space of the input image data depending on the printing conditions, the differences may be determined with respect to an entire colorimetric color space which is a color space of the colorimetric data to correct the image data depending on the proofer conditions using the determined differences, rather than correcting the colorimetric data.
Corrected colorimetric data in the colorimetric color space may be determined from the determined differences and the printing profile, the proofer profile may be corrected with the corrected colorimetric data, and the image data depending on the proofer conditions may be corrected with the corrected proofer profile. In this manner, a proof which matches a print as a target can be outputted from the proofer by only correcting the proofer profile without correcting the printing profile.
Corrected colorimetric data in the colorimetric color space may be determined from the determined differences and the printing profile, the proofer profile may be corrected with corrected colorimetric data produced by multiplying the determined corrected colorimetric data by a weighting coefficient depending on the colorimetric color space, and the image data depending on the proofer conditions may be corrected with the corrected proofer profile. In this fashion, the colors of a proofer can possibly be equalized more accurately with the colors of a print as a target.
According to
Fuji Photo Film Co. , Ltd.
Hilten John S.
Nolan, Jr. Charles H.
Sughrue Mion Zinn Macpeak & Seas, PLLC
LandOfFree
Color correcting method does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Color correcting method, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Color correcting method will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2579147