RGB to LUV converter

This RGB to LUV converter takes three sRGB channel intensities—red, green, and blue—each as an integer from zero through two hundred fifty-five, and returns CIE L*u*v* coordinates computed with the standard D65 white point used in web and imaging color workflows. Designers, color scientists, and developers use this mapping when a palette lives in eight-bit channels but the task needs a perceptual uniform space for distance measures, additive color models, or Luv-based analysis pipelines. The engine is fully deterministic: it inverse-compands each channel, multiplies by the D65 sRGB-to-XYZ matrix, forms CIE L* from relative luminance, then builds u* and v* from CIE u′v′ chromaticity against the D65 reference—never calling the network, sampling randomness, or depending on the clock.

How an RGB color turns into Luv values

In the eight-bit sRGB model used by CSS and most web graphics, each of red, green, and blue is an integer channel from zero through two hundred fifty-five. CIE L*u*v* rearranges that same stimulus into a lightness axis L* (roughly zero for black through about one hundred for diffuse white) and two chromatic axes u* and v* derived from the CIE 1976 u′v′ chromaticity diagram, which is often preferred when additive mixtures or uniform chromaticity distances matter more than Lab-style opponent axes.

Conversion first scales each channel by dividing by two hundred fifty-five, then undoes sRGB gamma (the IEC six-one-nine-six-six inverse companding curve) so the values become linear light. Those linear channels pass through a fixed three-by-three matrix into CIE XYZ under illuminant D65. Lightness L* is formed from relative luminance Y divided by Yn using the standard cube-root or linear CIE pivot.

Chromaticity uses u-prime equals four X over X plus fifteen Y plus three Z, and v-prime equals nine Y over the same denominator; u-star and v-star then equal thirteen times L-star times the difference from the D65 reference u-prime-n and v-prime-n. Pure black has undefined chromaticity in u′v′, so this engine sets u* and v* to zero when the XYZ sum term is zero. There is no path that accepts percentages or floating-point channels as input, and no silent clamp of two hundred fifty-six down to two hundred fifty-five.

Where RGB-to-Luv conversion fits in design, study, and software

Designers and imaging engineers meet this mapping when a brand or sensor pipeline lists RGB swatches and a workflow expects Luv targets, when chromatic distances should be reasoned about in a CIE u′v′-related space, or when a design system documents both screen RGB and Luv reference values side by side. Color scientists use L* with u* and v* when comparing additive mixtures, when preparing data for perceptual uniformity experiments, or when teaching the difference between opponent Lab axes and Luv chromaticity-derived axes.

Students see it in computer-graphics and colorimetry courses that introduce XYZ and then CIE 1976 spaces after sRGB, in digital imaging labs that move between channel sliders and perceptual coordinates, and in interview warm-ups that ask for a mental convert of a short triple. Pair it with Lab or multi-format color tools when you need other spaces, and with other free deterministic converters when you are building a small lab for color-system hygiene.