Improved methods to enhance the color perception for people with color vision deficiency / Mohd Fikree Hassan

Mohd Fikree , Hassan (2018) Improved methods to enhance the color perception for people with color vision deficiency / Mohd Fikree Hassan. PhD thesis, University of Malaya.

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Abstract

Color images are widely used to disseminate information in public places, on Web sites, and on smartphone applications. Moreover, millions of color images are also shared and used as a medium of communication among people. However, people with color vision deficiency are not able to discriminate certain colors and may thus misinterpret information. Elderly people also suffer from loss of color perception as a result of age. In this thesis, both color perception loss among the elderly people as well as those with red-green deficiency are studied. Recent clinical studies of color perception of the elderly show that as humans age, uniform yellowing pigmentation occurs on the human lens. In order to understand the effect of the uniform yellowing pigmentation, a mathematical formulation has been proposed in this thesis. The mathematical formulation uses the measured transmittance functions of the liquid-crystal display (LCD) and the spectral transmission factor of the human lens. Based on the values, three effective tristimulus ratios are computed, and the uniform yellowing pigmentation is simulated. The simulated uniform yellowing pigmentation is compared with the results of recent clinical studies for validation. The comparison shows that the simulated uniform yellowing pigmentation is in agreement with the results from these clinical studies. Using the uniform yellowing pigmentation, color perception of the elderly is simulated to three different types of images; MacBeth ColorCheckers color patches, synthesized and real images. The results of the simulated images show that as humans age, the images lose their bluish element and become yellowish. Furthermore, comparison with the non-uniform yellowing pigmentation methods show that the results from the proposed method are closer to the clinical data. Various image recoloring methods have been proposed by researchers to improve the color perception of people with red-green deficiency. However, the recolored images may look non-pleasing to people with normal color vision. Moreover, the recolored images may lose their naturalness. In addition, some of the recoloring methods utilize complex and iterative processes that may not be suitable for practical usage. This thesis proposes a much simpler and efficient recoloring method that enhances the color perception of people with red-green deficiency while maintaining the naturalness of the original images as much as possible. The proposed method utilizes the error and rotation parameters to recolor the images. Using this process, the recolored images have the same luminance and hue as the original images. Objective evaluation shows that the recolored images maintain the naturalness better than three other existing methods. A total of twenty six people, which includes fifteen people with normal color vision and eleven red-green deficients, took part in the paired comparison test. The results of the paired comparison test show that the proposed method achieves higher preference scores in terms of naturalness preservation and the overall preference.

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