Rainbow is a tool for studying perceptually uniform color scales. Given two colors chosen by the user, Rainbow creates color scales by interpolating between the end colors in RGB and CIELUV spaces, and displays the scales side by side for comparison and study. It can also display a plot of the luminance (L*), chroma (C*), or hue (huv) of each scale instead of showing the colors. This is useful for comparing the linearity of the two scales on each parameter (however, being just a polar form of the CIELUV space, L*C*Huv is only an approximation to a perceptually uniform color space).
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