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Chromatic adaptation is an important mechanism in the human visual system, which affects the perceived color appearance of scenes and objects under the illumination. Recent studies, however, found that the degree of chromatic adaptation was significantly affected by the chromaticities of the adapting condition, which is not characterized in the existing chromatic adaptation transforms and color appearance models. This work was carefully designed to investigate how the degree of chromatic adaptation needs to be considered to reproduce the overall color tone of scenes under the illumination having a wide range of chromaticities. Human observers viewed a scene under 85 light settings, and then adjusted the color appearance of the scene image shown on a smartphone display to match that of the physical scene. The adjustment of the image color appearance was achieved by performing chromatic adaptation transform with different image white points. The results clearly showed how the degree of chromatic adaptation varied with the illuminant chromaticities, and how the image white point should be adjusted to reproduce the color tone of an illuminated scene. [ABSTRACT FROM AUTHOR]

To help CVD (colour vision deficiency) observers distinguish among different colours in digital images, this study proposes a content‐dependent Daltonization algorithm based on lightness and chroma information. This improves the trade‐offs in contrast, naturalness, and colour consistency deficiencies found in existing methods. Chroma remapping and brightness adjustments on image content are utilized to increase contrast and maximize the preservation of the original hue. In a quantitative study, the proposed method proved more useful for dichromats than did existing methods. The evaluation by research subjects showed that the method was superior to the current methods in balancing contrast, naturalness, and colour consistency. [ABSTRACT FROM AUTHOR]

A new spectral reflectance estimation method based on CIE XYZ values under multi-illuminants was proposed to obtain multi-spectral images accurately by using digital still cameras. CIE XYZ values under multi-illuminants were initially predicted from raw RGB responses by using a polynomial model with local training samples. Then, spectral reflectance was constructed from the predicted CIE XYZ values via the pseudo-inverse method. Experimental results indicated that the new spectral reflectance estimation method significantly outperformed the traditional colorimetric characterization method without requiring extra training samples or greatly increasing computational complexities. © 2016 Wiley Periodicals, Inc. Col Res Appl, 42, 68-77, 2017 [ABSTRACT FROM AUTHOR]

In recent years, helping individuals with color vision deficiency to distinguish confusing colors in digital images, which is called Daltonization, is a hot topic. However, a number of Daltonization methods have a color reduction problem that causes unnatural image colors for normal color vision observers and those with anomalous trichromatic color vision deficiencies. A color-enhancing algorithm is proposed to make up for the shortage in color naturalness. Based on the conclusion in previous studies that colors confused in the same type of color blindness are approximately straight lines (called confusion lines) on the u ′ v ′ chromaticity plane and all of the confusion lines intersect at the same point (called the confusion point), we propose a polar coordinate transformation based on intersection points of confusion lines, which can transform chromaticity information into perceptually sensitive and perceptually insensitive color blindness information. From the two color-blind sensitive information of the Daltonized image and the one color-blind insensitive information of the original image, the three-dimensional information can be combined to obtain an enhanced image. The enhanced image has a similar color appearance of the Daltonized image under the perspective of dichromats and has a more natural and colorful color appearance under the perspective of anomalous and normal trichromats. In addition, we propose a lightness modification to reduce lightness errors between the enhanced images and the Daltonized images. The quantitative evaluation shows that the method proposed is effective but sacrificing a small amount of color contrast of the Daltonized images. [ABSTRACT FROM AUTHOR]