色貌模型在跨媒体图像复制中的应用研究

目的 研究CIECAM02和iCAM色貌模型颜色空间的均匀性,以及应用于不同观察条件下的图像复制效果。方法 利用均匀颜色数据集测试色貌模型颜色空间的均匀性,并通过视觉评价实验来测试2个色貌模型的图像复制效果。结果 CIECAM02的色貌空间具有更好的色差均匀性,iCAM的色貌空间具有更好的色相、明度和彩度均匀性。在不同观察条件下的图像复制中,CIECAM02有更好的表现。结论 iCAM的颜色空间适合于颜色色貌属性的计算,而CIECAM02的颜色空间更适合于颜色色差的计算,在不同观察条件下的图像复制中,CIECAM02有更稳定的表现,但并不是对所有图像都有更好的表现。     

基于Jab 空间的色差公式研究

在CIECAM02-Jab 的基础上,使用XUT 数据集对明度、彩度、色相进行了优化,修正了均匀颜色空间,并对色差公式进行了欧几里德化,建立了一个基于Jab 颜色空间的色差公式。检验结果表明,新的色差公式计算色差的性能较好,而且其具有一个均匀的颜色空间,形式更为简单。     

CIE94 CIEDE2000色差公式均匀性分析

利用孟塞尔(Munsell)颜色系统,在视觉上为等色差系统以及色调、彩度和明度可以单独改变的特性,选择明度V=5的色块,分别从色调、彩度两方面对CIE94、CIEDE2000色差公式的均匀性进行了研究.数据计算结果表明,它们计算出的色差值是比较一致的;但它们的均匀性是不同的.需要针对不同的彩度、色调选择使用不同的色差公式.     

基于OSA-UCS数据的CIECAM02图像复制色差评价

目的为了改进彩色图像复制时在不同观测环境下的误差,将优化后的色貌模型引入色彩信息转换。方法在分析CIECAM02-Jab用于彩色图像复制的色彩评价的基础上,提出利用OSA-UCS数据集建立新的优化色貌空间实验方案。利用线性回归的方法,调整原始颜色空间中的明度和彩度,构建出新的均匀颜色空间J_xa_xb_x。结果经过检验发现新的优化色貌空间J_xa_xb_x色差的离散程度减轻,空间更趋均匀,更加符合均匀性标准。结论新的优化色貌空间J_xa_xb_x修正了均匀颜色空间的均匀性,比CAM02初始色貌空间有了一定程度的提高,对彩色图像复制的色差评价取得了一定的效果。     

CIE色度坐标与Munsell颜色系统之间软件转换的实现

1孟塞尔颜色系统简介目前国际上广泛采用孟塞尔颜色系统（Munswllcolorsystem）作为分类和标定表面色的方法。它是从心理学的角度，根据颜色的视知觉特点所制定的颜色分类和标定系统。用一个三维空间的类似球体模型把各种表面色的三种基本特性：色调H，明度V，彩度C全部表示出来。立体模型中的每一部位各代表一个特定颜色，并给予一定的标号HV／C，用专用纸片或织物制成标准颜色样品，汇编成颜色图册。1943年美国光学会对孟塞尔颜色系统作了进一步研究，通过大量光谱光度测量和多达数万人的颜色视觉观察实验，重新编排和增补了原孟塞尔颜…     

基于CIEDE2000色差公式权重函数修正的研究

为了对CIEDE2000色差公式计算中等色差时的权重函数SL,SC进行修正,使计算结果与人眼的视觉感觉相一致,选用了孟塞尔(Munsell)颜色系统中的中等明度和中等彩度色块,在5R、5Y、5G、5B 4个主色调的颜色区域分别改变明度和彩度进行计算,改变彩度时共有34对样品,改变明度时共有25对样品,得到新的修正系数.用修正后的权重函数计算Munsell颜色样品和实验制作的改变明度和彩度的24对中等色差样品,验证了修正后的色差公式在计算中等色差时,色差公式的均匀性以及与人眼的视觉感觉的线性相关性都有了较大的提高,可用于对彩色印刷品的颜色评价.     

人眼明度视觉对比敏感度特性测量

目的 研究人眼明度视觉感受野“中心-周边”的拮抗特征。方法 设计心理物理实验,测量视觉感知颜色空间CIELAB明度轴上5个明度样本在11个空间频率上的对比敏感度数据;分别采用一元分析法和主成分分析法对实验采集数据进行分析,对比不同明度视觉、空间频率以及对比敏感度阈值之间的函数关系。结果 一元分析表明,5个明度样本的对比敏感度曲线表现为带通特性,明度值越高带通特性越明显;主成分分析表明,以前2个主成分为新变量,可描述人眼视觉感受野特性。结论 人眼视觉在低频1~6 cpd时表现出了“中心-周边”环绕的阶调传递特征;在高频时人眼明度CSF与亮度CSF相似,随着空间频率的升高,人眼视觉对比敏感度降低。     

金银卡纸的镜面反射对颜色复制的影响

目的针对金银卡纸表面因具有强烈的镜面反射作用且印刷适性较差的缺点,研究金银卡纸镜面反射对印刷品颜色的质量控制。方法试验分析金银卡纸印刷镜面反射作用对印品明度值的影响,用曲线拟合的方法找出包含和不包含镜面反射作用测出的明度值之间的关系。结果经过检验分析,SCE条件下的测量数据相对于SCI明度偏小,这是因为SCE测量模式中,镜面反射光被排除在外面,只测量了漫射光。从青色的线性拟合图来看,所得线性拟合图大致为一条斜率为45°的直线。结论包含和不包含镜面反射明度值这2组数据之间存在数学关系,在实际应用中,可以考虑使用明度差这种线性关系来作为金银卡纸颜色控制和评价的依据。     

CIE 1976LAB色差公式的均匀性研究

介绍了CIE 1976 LAB色度椭圆,并在中国颜色体系的基础上,分别从色相、明度、饱和度的角度对ΔE*ab的均匀性进行了研究.结果表明,该色差公式明度的均匀性较好,色相、饱和度的均匀性较差,该公式不能够很好地反应人眼的视觉感受.     

跨媒体颜色再现方法的研究

总结了跨媒体复杂图像颜色再现方法的研究现状及发展方向,介绍了基于空间视觉的颜色再现、基于CIECAM02的颜色再现和基于图像色貌模型3种方法的研究内容及发展趋势;着重分析了跨媒体颜色再现的难点和突破点,应用前景方面的优势和显著的实际应用价值.     

Computation and visualization of the MacAdam limits for any lightness, hue angle, and light source

We present a systematic algorithm capable of searching for optimal colors for any lightness L* (between 0 and 100), any illuminant (D65, F2, F7, F11, etc.), and any light source reported by CIE. Color solids are graphed in some color spaces (CIELAB, SVF, DIN99d, and CIECAM02) by horizontal (constant lightness) and transversal (constant hue angle) sections. Color solids plotted in DIN99d and CIECAM02 color spaces look more spherical or homogeneous than the ones plotted in CIELAB and SVF color spaces. Depending on the spectrum of the light source or illuminant, the shape of its color solid and its content (variety of distinguishable colors, with or without color correspondence) change drastically, particularly with sources whose spectrum is discontinuous and/or very peaked, with correlated color temperature lower than 5500 K. This could be used to propose an absolute colorimetric quality index for light sources comparing the volumes of their gamuts, in a uniform color space.     

Performance of recent advanced color-difference formulas using the standardized residual sum of squares index

The standardized residual sum of squares (STRESS) index was used to reevaluate four experimental datasets employed during the development of CIEDE2000, the current CIE recommended color-difference formula. This index enables statistical inferences not achievable by other metrics used commonly for performance evaluation. It was found that CIEDE2000 was statistically superior at a 95% confidence level to either CIE94, the previous recommended equation by the CIE, or the simple Euclidean distance in CIELAB, DeltaE*ab. Recent formulas based on the CIECAM02 color-appearance space and chroma-compressed variants of CIELAB were also evaluated and found to have only slightly reduced performance compared with CIEDE2000. These formulas have the advantage of simplicity and easier interpretation when used for quantifying color accuracy. Finally, each experimental dataset was evaluated separately rather than weight averaged as used during the development of CIEDE2000. Significant differences were found between datasets, suggesting that combining datasets may obscure important differences and that the practice of parameter optimization during formula development using combined data is likely suboptimal.     

基于CIECAM02的实时色彩转换模式

从当今包装印刷行业色彩管理的应用现状出发,论述了现今作为国际标准的ICC色彩管理模式的原理及其局限性,然后根据其局限性和当今时代的要求提出了一种改进的色彩转换模式--基于CIECAM02色貌模型的实时颜色转换模式.该模式可以使得包装印刷中对图像颜色信息更加准确地传递,并且真正意义上地实现颜色复制的跨媒体性.     

Relative significance of the terms in the CIEDE2000 and CIE94 color-difference formulas

CIELAB-based color-difference formulas are used to improve the prediction of visually perceived color differences through the introduction of various corrections to CIELAB. In our study we analyze the relative importance of these corrections. From the combined dataset employed for the development of CIEDE2000, we found that the improvement of CIE94 over CIELAB was considerably greater than that of CIEDE2000 over CIE94. Chroma-difference correction was the most important correction in both CIE94 and CIEDE2000. With an arbitrary value of 100 assigned to this correction, the score of the hue-difference correction in CIE94 was 21, and the scores of the four remaining corrections in CIEDE2000 were as follows: hue difference, 29; rotation term, 8; lightness difference, 8; and gray correction, 6. At 95% confidence level each of the corrections introduced in CIEDE2000 or CIE94 was statistically significant for the whole combined dataset, in agreement with the results reported by CIE TC 1-47 and 1-29. For the combined dataset, the differences between CMC and CIEDE2000 were found to be statistically significant at 95% confidence level, but the differences between CMC and CIE94 were not. From subsets of the combined dataset it was concluded that further analyses of the lightness-difference and gray corrections proposed by CIEDE2000 would be desirable, using new experimental data.     

A chromatic diversity index based on complex scenes

We propose a chromatic diversity index based on the Munsell set capable of predicting illuminant induced changes in chromatic diversity of complex scenes. The color differences between complex scenes derived from hyperspectral data under a test and under a reference CIE D65 illuminant were computed and compared with the corresponding differences for the Munsell set. It was found that the average color difference between the complex scenes correlates well with the color differences of the Munsell samples with an average correlation of about 0.94, a result indicating that the Munsell set can be used to predict chromatic changes in complex scenes.