尽管自然场景中自然发生了全球和局部日光变化,人类视觉系统通常很好地适应这些变化并形成稳定的颜色感知。在之前的研究中,分析了以相关色温(CCT)为特征的日光对不同色度描述符的影响(Ojeda等人。,2017)。结果表明,对于超过14,000K的CCT值,色度信息几乎是恒定的,局部极值发生在低CCT范围内。这项工作的目的是将对光源的CCT依赖性的分析扩展到考虑空间色结构的那些,包括二阶描述符(梯度,光谱斜率,光谱特征,和PCA)和高阶描述符(峰度,偏斜度,和相关颜色的数量)。我们的结果表明,对于15,000K以上的CCT和3,900K-9,600K范围内的局部极值,大多数描述符表现出水平渐近行为。对于可以在CIELAB空间中分析的描述符,获得了足够的统计证据来考虑偏度,峰度,并且L*通道的独立频谱斜率在所使用的CCT范围内相等。然而,当将PCA应用于图像块时,光谱特征和主成分的方向的微小变化在统计上不显著,并且在不同的光源下不能被认为是相等的。相关颜色(NRC)的数量表现出对温度变化的敏感性,其行为与其他描述符相似。由于数量少。
Despite the natural occurrence of global and local daylight changes in natural scenes, the human visual system typically adapts well to these changes and develops stable colour perception. In a previous study, the influence of daylight characterized by its Correlated Colour Temperatures (CCT) on different chromatic descriptors was analysed (Ojeda et al., 2017). The results showed that chromatic information is almost constant for CCT values above 14,000 K, with local extremes occurring in the range of low CCTs. The aim of this work is to extend the analysis of the CCT dependence of the illuminant to those that consider the spatio-chromatic structure, including second order descriptors (gradients, spectral slope, spectral signature, and PCA) and higher order descriptors (kurtosis, skewness, and number of relevant colours). Our results show that most of the descriptors exhibit horizontal asymptotic behaviour for CCTs above 15,000 K and local extremes in the range of 3,900 K-9,600 K. For those descriptors that could be analysed in CIELAB space, sufficient statistical evidence was obtained to consider skewness, kurtosis, and the independent spectral slopes of the L* channel as equal in the range of CCTs used. However, the slight variations in spectral signatures and the directions of the principal components when applying PCA to image patches are not statistically significant and cannot be considered equal under different illuminants. The number of relevant colours (NRC) exhibits sensitivity to temperature variations and behaves similarly to the other descriptors, due to its small number.