Discussion on the Application of CIE's Latest Color Table Model (I)

[Abstract] The color table model can solve the problem of real reproduction of different media in different observation conditions, different backgrounds and different environments. This article describes in detail the latest international color table model CIECAM97 and its revised version CIECAM02, in order to facilitate the correct application in the printing industry in the future.

Keywords: color table model; CIECAM97s; CIECAM02; color space

Since the International Lighting Association (CIE) recommended the CIELAB color space and its color difference formula in 1976, this formula has been widely used in the quality control of the textile printing and dyeing industry. However, due to the inherent visual inhomogeneity of the color space, there are some problems in the consistency between the visual results and the calculation results. As an extension of traditional colorimetry, the use of a color table model can predict the color appearance of color stimuli under different viewing conditions. It gives parameters related to visual attributes, such as brightness, saturation, and hue, which can be used in numerical colors. It plays an important role in applications such as copying and light source color rendering evaluation.

1 CIECAM97s color table model

In order to establish a high-performance color table model, in May 1997 in the first branch of the CIE meeting, a unified simplified version of the color table model CIECAM97s (Color Appear) was proposed by the TC1-34 (in charge of the color table model inspection and evaluation) group. .ance Model 97s) as its first color table model that was adopted and proposed for general use. CIECAM97s is based on the evaluation of various existing color table models and combines the advantages of various models. It has better uniformity and consistency of color differences and observation results.

1.1 Uniformity of the color space in the model

When creating color space, Luo M. of Derby University, UK R. The professor selected the color description quantities o (redness and greenness), b (yellowness and blueness), J (lightness), c (saturation), and h (hue angle) in the CIECAM97s color table model. Two initial color spaces Ja1b1 and Ja2b2 are established respectively.

In Table 1, the standard deviation of the size of the ellipse, the average flattening ratio, and the standard deviation of the flatness are the indexes for measuring whether the chromaticity plane is uniform. The table shows that a1 - b1. The standard deviation of the dimensions on the plane and the standard deviation of the flatness are the smallest, and the average flatness of the a-b: ellipse on the plane is the smallest. In addition, all indicators of the a1 -b1 plane are smaller than the corresponding indicators of the a -b plane, which indicates that the chromaticity plane of the Ja1b1 space is more uniform than the chromaticity plane of the CIELAB.

1.2 New Color Difference Formula Based on CIECAM97s

The color difference formula of CIECAM97s is as follows:

(to be continued)