SCS — Module 01 - Read a Color in lRGB Mode

Read a Color with the ℓRGB Mode

R, G, B choose a simplex direction. Saturation moves away from gray along that direction. Luminance is relative to the maximum allowed for that direction.

Hex#000000

Luminance ℓ / ℓmax(direction)

78.0%

R (π₃)

V (π₅)

B (π₇)

Saturation / Smax(direction)

72.0%

This mapping is intentionally constrained: luminance is relative to what the chosen simplex direction can actually display inside sRGB.

Forme simplex (ℓ ; R, G, B)

R, G, B are normalized simplex weights. They define a chromatic direction, not display RGB values.

Forme polaire (ℓ ; S, θ)

S is shown here as a relative saturation along the chosen simplex direction.

Luminance ℓ

Max luminance on direction

R (π₃)

V (π₅)

B (π₇)

Relative saturation

Exact S = DKL(π||u)

Chromatic entropy L

Chromatic budget S+L

Hue angle

Relative saturation

Luminance ℓ

Chromatic entropy L

Theory

The mapping is built in four steps: R,G,B → πdir, then a relative saturation slider moves from gray u=(1/3,1/3,1/3) toward that direction, then luminance is applied only as a fraction of the maximum luminance allowed by that direction inside the sRGB gamut, and only then the color is converted for display. This avoids the unstable behavior caused by trying to impose absolute luminance independently of chromatic direction.