Modification Of Chromatic Adapation And Simultaneous Colour Contrast Effect In Colour Appearance Model

The core of cross-media colour reproduction technology is the colour appearance model,and the extensive usage of multimedia device has prompted the development of colour appearance model.The goals of the work were to verify the chromatic adaptation and to extend simultaneous colour contrast function in colour appearance model.The first goal was covered by two subprojects.The first was to use the memory colour matching method to investigate the chromatic adaptation.The effect was studied under different lighting conditions which were varied in CCT and luminance level.The relationship between the degree of the chromatic adaptation and the parameters of the lighting conditions were studied.And a new CAT which can be applied to self-luminous display was established.The memory colour and unique hue were taken as internal references to reduce the time to achieve full adaptation.And the images were used instead of patches to simulate a real scene.Two psychophysical experiments were carried out,and 2,000 matchings of corresponding colours were accumulated.The results showed CCT did affect the degree of chromatic adaptation significantly,with a lower degree under the adapting condition at a lower CCT,which revealed the weakness of CAT02.The optimized degrees of chromatic adaptation factor for the adapting conditions generally corroborated the trends that were found in other recent studies.In addition,the results also suggested that the Hunt effect may be over predicted in CAM02-UCS and CAT02.The second subproject was to use the magnitude estimation method to investigate the chromatic adaptation under extreme chromatic lighting conditions.The locations of the lightings on CIE1976 u'v' plane were close to the spectrum locus,so the colour purity was far beyond the previous studies.Two psychophysical experiments were carried out,and 1,470 estimations of corresponding colours were accumulated.The results showed that CAT 16 gave a good prediction performance for all the chromatic lightings except for blue lighting,and the degree of adaptation was relatively high,that is,D was close to 1.The second goal was the study of simultaneous colour contrast effect,to study the foreground/background colour effect.The first comprehensive simultaneous colour contrast effect model considering all the colour attributes based on the CAM16 was established,which is called CAM16 colour contrast(CAM16cc)model.And the influences of the shape of the pattern and the size of field of view were also investigated.The Albers' pattern was used to investigate the contrast effect.By refining the CAM 16,CAM16cc model was developed by enhancing the colour attributes instead of revising the structure of present model.This maintained the advantages of CAM 16.Four psychophysical experiments were carried out,and 67,998 ses of visual data were accumulated.The results clearly showed that the lightness of the target colours decreased with the lightness of the background colours.The intensity of the effect was significantly higher when the lightness of the background was higher than that of the target color.It was found that the contrast effect on chroma was similar to lightness with a smaller magnitude.And the direction of the hue contrast was in the opposite direction to the background colours and followed the opponent-colour theory.Also,the hue contrast was enhanced when the background colour was close to the target colour.The shape of the pattern had little influence on the contrast effect,and the influence of the field of view was mainly depending on the width of the border of the pattern.A reduction of the field of view would increase the intensity of the contrast effect.Finally,a large-scaled experiment was carried out via internet using categorical judgment method.The goal was to obtain a visual dataset in terms of colour difference to test the colour contrast model.The dataset was named as CC2020z dataset.The results showed that the CAM16cc model can accurately predict the contrast effect on all the colour attributes and also the cross-term effects.The CC2020z serves as an important public dataset to support the research in this field.