On the basis of K/S theory, tristimulus values can also be matched, but it is necessary to establish a database of K/S values and concentrations in sections to study the relationship between tristimulus values and concentrations, that is, the relationship between tristimulus values and dot percentage. In printing, the conversion methods between tristimulus value and dot percentage mainly include Neugebauer equation conversion, matrix conversion and lookup table conversion. In this paper, the conversion lookup table is established by chromatography. According to CIE standard chromaticity system, any natural color can be represented by spectral tristimulus values X, Y and Z. At present, most advanced colorimeters choose this chromaticity system, that is, the color of any object can be represented by tristimulus values X 10, Y 10, Z 10. The principle of computer color matching mainly uses the principle of metamerism, that is, if the tristimulus values of two color samples are equal, they are the same color.
The lookup table established by chromatography describes the relationship between tristimulus value and dot percentage of each color ink. Suppose a color sample is printed with three inks, A, B and C, and the dot percentages of these three inks are L, M and N respectively, then the ratio of A, B and C is L: M: N, and Bai Mo accounts for (1-L)+(1-m)+(/kloc-). This color matching system uses the data of CIE standard light source D65 and the field of view of 10, and uses CIELAB color difference formula: Δ eab = [(Δ L) 2+(Δ A) 2+(Δ B) 2]1/2 to calculate the color difference between the standard color sample and the color matching sample.
We can see that computer color matching with tristimulus values can make the colors of color samples under specific light sources appear in the form of data, and there is a corresponding relationship between tristimulus values of color samples and ink ratio, so whether the formula meets the requirements can be calculated through color difference test. Input the tristimulus value of each color block and the dot percentage of each ink into a computer to establish a basic database. When matching colors, the tristimulus value of the target color sample is input into the system, and the system calculates the mixed ink and its proportion, and outputs the formula prediction result. When the ink sample with color matching results is dried, the tristimulus values are measured, and the computer calculates the advantages and disadvantages according to the color difference formula, and makes further correction instructions, so that higher quality metamerism colors can be prepared quickly.
In terms of the quality requirements of color reproduction, according to the clear requirements of national standards for the color difference Δ e * ab of the same batch of color decorative prints, this paper chooses Δ e * ab ≤ 3.
Chromatograms include the most common colors. For the colors in the chromatogram, we can directly find the ink ratio, and for the colors that are not in the chromatogram, we can first find the color with the smallest color difference in the chromatogram, and then solve it by linear interpolation.