An image of W × H pixels (Width × Height) is represented by a three-dimensional matrix with size W × H × 3. The W and H values define the pixel and the third dimension holds the color of the pixel given by the R, G, B values of the color. A metric of the difference in color between two colors is the distance of the two colors in the RGB space. The greater the distance between the two colors, the larger the contrast between the two colors. In the context of this study, the greater the distance between a predominant color in the worksite and the color of HVSA, the more conspicuous a person will be. The simplest measure of the distance between two colors in the RGB space is the Euclidean distance:
Besides RGB color space, there is one more color space of particular importance for this study, the CIE Lab color space (luminance, red-green and blue-yellow). The advantages and disadvantages of each color space are discussed in ….. Brieﬂy, CIE Lab is a perceptually uniform, with the distances between colors in CIE Lab-space reﬂecting the degree of the perceived difference between those colors by human color vision. RGB, on the other hand, is largely optimized for digital displays as it represents the mixing of different amount R, G, B color to produce the other colors.Three available color spaces in color distance are CIE Lab (luminance, red-green, and blue-yellow channels), RGB (red, green, and blue channels), and HSV (hue, saturation, and value channels).