Preset Functions for Color Vision Deficient Viewers. The use of color is an important aspect of computer interfaces. Designers are keen to use

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1 Some Student November 30, 2010 CS 5317 Preset Functions for Color Vision Deficient Viewers 1. Introduction The use of color is an important aspect of computer interfaces. Designers are keen to use color to convey information, but often ignore the population of color deficient viewers [Huang et al. 2008]. In the United States, eight percent of men and 0.8 percent of women have a deficit in their color vision [Wang et al. 2009]. This means that one in 20 people have difficulty with computer interfaces due to color usage [Wang et al. 2009]. Colors that are seemingly contrasting and perceptible to a normal color viewer can appear less so to a color deficient user. The human eye sees color by the absorption of light by two kinds of photoreceptor cells: rod cells and cone cells [Jefferson, L. and Harvey, R. 2007]. The rods are located in the peripheral retina and are active in low light [Jefferson, L. and Harvey, R. 2007]. The cones are located in the center of the retina and enable us to perceive color during daylight [Jefferson, L. and Harvey, R. 2007]. They are three kinds of cones: red, green, blue [Brettel et al. 2007]. Each cone contains a different pigment and activates when the pigments absorb light [Brettel el al. 1997]. Color deficiencies occur when one or more cones are malfunctioning or not functioning at all. There are different variations of color deficiencies but the general common terms are red-green and blue-yellow [Brettel et al. 1997]. The most prevalent is red-green which makes up 99 percent of color deficient viewers [Jefferson, L. and Harvey, R. 2007]. With the probability of one in 20 people visiting a Web site having some form of color deficiency, there are guidelines and automatic tools that assist Web designers to make their Web

2 Preset Functions for Color Vision Deficient Viewers 2 pages friendly to color deficient viewers. For example, the World Wide Web Consortium (W3C) has established general principles for developers to use and the automated tools accommodate color deficient viewers perception of graphical images. Yet, no automatic tool is a fit for all color deficiencies and most focus to provide a solution for easier visibility of Web pages. Color deficiency does not end at Web sites. Computer interface designers do not take into consideration color deficient viewers, despite the relatively high incidence of color deficient viewers [Wang et al. 2009]. In this technological age, it is imperative to give color deficient viewers an opportunity to change the color scheme of the entire operating system according to their own deficiency. This would enable them to better interact with interfaces and facilitate the visibility of color content. Therefore, my question is, can the operating system have preset functions that modify the color and brightness of the window to improve the usage of computer interfaces for color deficient viewers? The remainder of this paper describes human color perception and various types of color vision deficiency (Section 2). Section 3, reviews the different tools available for Web developers to accommodate color deficient viewers and drawbacks. Section 4 briefly describes propose methodology and conclusions are drawn. 2. Color vision deficiency (CVD) Color deficient viewers experience loss of information due to the lack of not being able to differentiate colors. The absorption of photons by three different types of photoreceptor cells, the cone cells, permit color vision. Cone cells have three classes of cones, each containing a different pigment, S-cones (blue), M-cones (green), and L-cones (red) [Huang et al. 2008]. Color vision deficiency (CVD) results from partial or complete loss of function of one or more types of cone cells [Huang et al. 2008].

3 Preset Functions for Color Vision Deficient Viewers Color perception A normal color viewer (trichromatic) would observe all perceivable colors. The signals from the three cones allow the brain to translate vision into a wide range of colors. However, viewers with CVD are not capable of experiencing all possible colors due to their abnormal color vision system. They are three main types of CVD: anomalous trichromatism, dichromatism, and monochromatism [Jefferson, L. and Harvey, R. 2007]. Anomalous trichromatism is the mildest form of CVD [Jefferson, L. and Harvey, R. 2007]. It occurs when one of the cone cells has had its peak sensitivity shifted so that the pigments in one type of cones are not sufficiently distinct from the pigments in another type [Huang et al. 2008]. Anomalous trichromats are classified as protanomaly, deuteranomaly, tritanomaly depending on which cone has shifted [Jefferson, L. and Harvey, R. 2007]. Dichromatism is a severe form of CVD where one of the cone types is missing [Huang et al. 2008]. Dichromats are classified as protanopes (lack of red cone), deuteranopes (lack of green cone), or tritanopes (lack of blue cone) [Jefferson, L. and Harvey, R. 2007]. Protanopes and deuteranopes are unable to distinguish between colors in the green, yellow, red section of the spectrum, while tritanopes have difficulty in discriminating blue from yellow [Huang el al. 2008]. Monochromatism is the severest and rarest class of CVD [Huang et al. 2008]. Monochromats are also known as total color blindness because they lack all types of cone cells. They are not able to distinguish any colors and can perceive brightness variations only. An example of their vision would be a black and white television.

4 Preset Functions for Color Vision Deficient Viewers 4 3. Web tools to accommodate CVD viewers The use of colors in multi-media contents to convey rich visual information has increased over the years [Huang et al. 2008]. Most Web sites only aim to serve normal vision viewers without taking into account CVD viewer [Wang et al. 2009]. However, there are numerous guidelines and automatic tools available for designers to accommodate CVD viewers. 3.1.Guidelines There are general guidelines based on experience and best practice [Jefferson, L. and Harvey, R. 2007] for Web developers to abide by to accommodate CVD viewers. The guidelines attempt to ameliorate the specific visual problems related to poor color selection. For example, the World Wide Web Consortium (W3C) has established general principles for Web developers to use [Chisholm et al. 2001]. Most guidelines advice to use a restricted CVD palette or verification color schemes to accommodate CVD viewers [Jefferson, L. and Harvey, R. 2007]. However, guidelines have obvious problems. Guidelines do not take into consideration the different variations of CVD and the task to accommodate all viewers would take a lot of effort for designers. Also, there is no single set of design guidelines that are comprehensive and there is room for interpreting what is the best way to design a friendly CVD Web site [Troiano et al. 2008]. 3.2.Automatic Web tools Several automatic tools assist Web developers to create friendly pages for CVD viewers. Each tool uses different algorithms to approach how to offer CVD viewers better usability of multi-media content but do not provide interface solutions. Thes tools aim to simulate images according to the deficiency of the CVD viewer. For example, the Daltonizing algorithm presents a tool to allow users to specify three parameters to re-color images. The first parameter is for

5 Preset Functions for Color Vision Deficient Viewers 5 stretching contrast between red and green hues, the second one is for blue and yellow contrast modulation, and the last component is modulating luminance [Dougherty, R. and Wade, A.]. The tool is available online and can be incorporated to other applications. The results of the images are sensitive to the selection of the parameters and improper parameters can result in unnatural images [Dougherty, R. and Wade, A.]. Another approach includes the usage of replacement color-maps that allow a designer to check which colors are visible to dichromats [Viénot et al. 1999]. Most approaches modulate colors to give discrimination between different colors or give CVD viewers the same magnitude as that perceived by a normal color viewer [Jefferson, L. and Harvey, R. 2007]. These schemes provide solutions to the problem of adapting images for CVD viewers in Web pages but none is widely use despite the fact that color-related accessibility is a problem to one of 20 viewers of a Web site [Wang et al. 2009]. The guidelines are either arduous to designers or publicized schemes only produce acceptable solutions for particular CVDs. Color deficient users not only have problems viewing Web pages but also personal graphical content on the desktop. To lessen the burden to Web developers and provide a universal tool for CVD viewers, my question is: can the operating system have preset functions that modify the color and brightness of the window? 4. Conclusion Color content in Web pages do not take into consideration color vision deficiencies [Wang et al. 2009] There are various types of color deficiencies and each deficiency has a different perception of color. Color deficiencies guidelines can assist a Web developer to create a colorblind friendly Web site but trying to accommodate all color deficiencies is cumbersome to

6 Preset Functions for Color Vision Deficient Viewers 6 Web developers [Troiano et al. 2008]. On the other hand, automated tools only address certain aspects of color deficiencies and do not provide a universal design. To provide a universal solution for color vision deficiencies, programmed functions are going to be implemented into the operating system. The functions will modify the screen color according to the selection. An experiment with various CVD viewers will test the effectiveness of the functions to modify color content to the color deficiency selected. The effectiveness will be rated according to how well the programmed functions modified the colors and CVD viewers to perceive the color content presented in the operating system. I expect that the preset functions will successfully modify color content to accommodate CVD viewers.

7 Preset Functions for Color Vision Deficient Viewers 7 References Brettel, H., Viénot, F., and Mollon, J.D. (1997) Computerized simulation of color appearance for dichromats, Journals of Optical Society of America, Vol. 14, Issue 10, Chisholm, W., Valderheiden, G., and Jacobs, J. (2001) Web content accessibility guidelines 1.0. World Wide Web Consortium, interactions 8, Huang, J., Wu, S., and Chen, C. (2008) Enhancing Color Representation for the Color Vision Impaired. Dans Workshop on Computer Vision Applications for the Visually Impared, Jefferson, L. and Harvey, R. (2006) Accommodating Color Blind Computer Users. Proceedings of the 8 th international ACM SIGACCESS conference on Computer and accessibility, Portland, Oregon, USA, October 22-25, Troiano, L., Birtolo, C., and Miranda, M. (2008) Adaptign Palettes to Color Vision Deficiencies by Genetic Algorithm, Proceedings of the 10 th annual conference on Genetic and evolutionary computation, Atlanta, Georgia, USA, July 12-16, Wang, M., Liu, B., Yang, L., and Hua, X. (2009) Accessible Image Search for Colorblindness. ACM Transactions on Intelligent Systems and Technology, Vol. 1, Issue 1, Viénot, F., Brettel, H., and Mollon, J. (1999) Digital video colourmaps for checking the legibility of displays by dichromats. Color Research and Application Vol. 24, Issue 4,

VISUAL SIMULATING DICHROMATIC VISION IN CIE SPACE

VISUAL SIMULATING DICHROMATIC VISION IN CIE SPACE Yinghua Hu School of Computer Science University of Central Florida yhu@cs.ucf.edu Keywords: Abstract: Dichromatic vision, Visual simulation Dichromatic