JP3184262B2 - How to create RGB color database - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates generally to a database, and more particularly to an RGB color database useful for color reproduction processing and a method for creating the same. The present invention relates to the invention described in the same-named patent application (reference number 00003144) “Color separation method”.

[0002]

2. Description of the Related Art In a current color separation process , a display device such as a CRT color monitor is used to display a color image to be finally printed using cyan, magenta, yellow, and black printing inks. Tristimulus value, the color phosphorescent value of the display monitor, the gamut of the printing inks, X
- when plotted on Y C IE chromaticity diagram, it is well known that no coextensive. The usefulness of a color display monitor as a print predictor and as an image modifier is limited by the non-identity of the three color gamuts . Chromaticity range in the chromaticity gamut and the print ink on a color display does not have the same spread, it does not completely overlapped, by performing adjustment between the color obtained from the color and the printing ink to be displayed on the monitor appropriately to each other Need to bring about relationships.

[0003]

SUMMARY OF THE INVENTION It is therefore a general object of the present invention to provide an RGB color database and a method for creating the same.

A more specific object of the present invention is to provide a color database which establishes a color relationship between the gamut of the RGB primary colors of the display and the gamut of the printing ink.

[0005] A further object of the present invention, the virtual primaries R, including both chromaticity gamut of printable ink chromaticity gamut and the display device ', G', by defining the three chromaticity gamut of B ' is there.

[0006]

An RG of a display device is provided.
Chromaticity gamut of B primaries and the chromaticity gamut of printable inks, creating a RGB color database by referring to the triangular chromaticity gamut of the defined virtual primaries R'G'B '. In the triangular chromaticity range ,
Both the gamut of the printable ink and the gamut of the display device are included. The virtual R'G'B 'primaries are located on the extensions of each of the three lines connecting the neutral chromaticity point and the RGB primaries of the display device. Color data is R'G'B '
An RGB color database is generated by defining virtual primary colors.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG.
Primary color, C, M, Y, CM, CY of the printing ink to be measured
FIG. 4 is a CIE type XY chromaticity diagram showing positions of MY primary colors, virtual R′G′B ′ of an RGB database, and CM ′, CY ′, and MY ′ virtual primary colors of printing ink. The primary colors of the color display device define triangular RGB with neutral chromaticity points indicated by the letter “N” in FIG. Chromaticity of printing ink
The area is an area limited by C, M, Y, CM, CY, and MY points.

[0008] The virtual database primaries R'G'B 'are defined starting from the neutral chromaticity point N and extending three lines passing through the display primaries R, G, B. The virtual database primary color R'G'B 'is the chromaticity of the color display
Area (RGB) and the chromaticity area of the printing ink (C, M, Y, C
M, CY, define a triangular chromaticity gamut that includes both MY).
The location of the database virtual primaries R'G'B 'can be found along the line segments NR, NG, NB beyond the point shown in FIG. 1, but with the size of the RGB database of a given image. To achieve the concomitant minimization, it is desirable to minimize the triangular area defined by the virtual database primaries R'G'B '. Accordingly, as shown in the figure, the triangular chromaticity region of the virtual database primary colors R'G'B 'includes the primary colors C, Y, and M of the ink on its sides.

Referring to FIG. 1, the primary colors CM of the printing ink,
The saturation levels of CY and MY are calculated based on the virtual primary colors CM ′, CY ′ and M
It can be seen that Y ′ is increased without changing the hue of the primary color. The CY ′, CM ′ virtual primary colors are on extensions of the N-CY, N-CM lines as shown by the dotted lines in the figure. The effect of the increased saturation of the CM, CY, and MY primaries is that calibration can be performed for a "virtual" print process that has a wider saturation range than the actual print process . Assuming increased saturation of the CM, CY, and MY primary colors, it can be seen that there is a trade-off in that the saturation of colors having a hue determined by CM, CY, or MY is slightly reduced. However, this unsaturation is much less problematic than the shade transitions caused by CMYK reduction of oversaturated colors. Global unsaturation for those shades is preferred over the "projection" method, in which gamut colors outside of saturation are projected into the printable saturation region , since the global unsaturation approach leaves a saturation difference. This uses a set of "virtual" colors associated with Neugebauer coefficients and primary colors.
For a detailed description of the processing , see “Color Separation Method” in the related application mentioned above.
And its contents are incorporated here for reference.

Having described in detail the embodiments of the present invention, numerous modifications will now occur to those skilled in the art without departing from the scope of the invention as defined by the appended claims. it is whether Akira et al. can be.

[Brief description of the drawings]

[1] chromaticity gamut of the RGB primaries of the display device, the chromaticity gamut of the printing inks, the RGB database virtual R'G '
Illustrates the chromaticity range of the B 'primary color in the form of a CIE chromaticity diagram (xy chromaticity positions of primary colors (c, m, y) and secondary ( cm, cy, my) virtual colors compared to measured values) It is.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-63-132592 (JP, A) JP-A-6-98182 (JP, A) JP-A-2-73257 (JP, A) JP-A-60-1985 168146 (JP, A) JP-A-56-161271 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H04N 1/46-1/62 G09G 5/02 H04N 9/00 G03F 3/10

Claims (1)

(57) [Claims] 1. A color display device and printing ink
In the method of creating an RGB database used in the above, the method comprises the steps of: defining a chromaticity gamut of RGB primary colors of a color display device; defining a chromaticity gamut of printing ink primary colors; Defining a triangular chromaticity gamut of virtual primaries R′G′B ′ that includes both the chromaticity gamut and the color gamut of the color display device (virtual R′G′B ′ primaries are neutral chromaticity points and color a display device chromaticity gamut are on each of the three lines extending connecting the RGB primary colors), by defining the color data for the R'G'B 'virtual primaries
How to create a RGB database, which comprises a stage of generating the RGB database.