The avatar for @sebastien
Sébastien Pierre
Using Observable for software engineering, programming language and user interface research.
Public
Edited
Nov 20, 2022
Importers
7 stars
Insert cell
Insert cell
Insert cell
Insert cell
Insert cell
Insert cell
Insert cell
Insert cell
Insert cell
Insert cell
Insert cell
Insert cell
Insert cell
Insert cell
grey = ([r,g,b]) => gamma((degamma(r) + degamma(g) + degamma(b))/3)
Insert cell
md`Let's try that approach and compute a grey value averaging the three component across the gradient, the first in gamma space and the second in linear space.`
Insert cell
Insert cell
Insert cell
Insert cell
luma = ([r,g,b]) => 0.2126*r + 0.7152*g + 0.0722*b
Insert cell
Insert cell
luminance = ([r,g,b]) => 0.2126*degamma(r) + 0.7152*degamma(g) + 0.0722*degamma(b)
Insert cell
Insert cell
lightness = (rgb)=>{
// This is from: https://stackoverflow.com/a/56678483/4100249
const y = luminance(rgb)
return (y <= (216/24389) ? y * (24389/27) : Math.pow(y,(1/3)) * 116 - 16) / 100.0
}
Insert cell
Insert cell
Insert cell
Insert cell
Insert cell
Insert cell
Insert cell
Insert cell
Insert cell
Insert cell
Insert cell
Insert cell
Insert cell
Insert cell
Insert cell
Insert cell
Insert cell
Insert cell
Insert cell
Insert cell
Insert cell
Insert cell
Insert cell
Insert cell
Insert cell
Insert cell
huedistance = (a,b) => {
const d = Math.abs(hue(a) - hue(b))
return 2 * (d > 0.5 ? 1 - d : d)
}
Insert cell
Insert cell
hsl(hex(HSLColor))
Insert cell
viewof HSLColor = color()
Insert cell
saturation = rgb => hsl(rgb)[2]
Insert cell
Insert cell
Insert cell
Insert cell
Insert cell
Insert cell
Insert cell
Insert cell
Insert cell
Insert cell
Insert cell
Insert cell
Insert cell
Insert cell
Insert cell
Insert cell
Insert cell
Insert cell
Insert cell
Insert cell
Insert cell
Insert cell
Insert cell
Insert cell
Insert cell
degammasRGB = _ => _ <= 0.04045 ? _/12.92 : Math.pow( ( _ + 0.055) / 1.055, 2.4)
Insert cell
gammasRGB = _ => _ <= 0.0031308 ? _ * 12.92 : 1.055 * Math.pow(_, 1.0/2.4) - 0.055
Insert cell
md`Note that according to the [WCAG](https://www.w3.org/TR/WCAG21/#dfn-relative-luminance), the gamma expansion threshold is different in sRGB, from 0.04045 (what we have in *degammasRGB*) to 0.03928, however that difference should have a negligible impact.`
Insert cell
Insert cell
Insert cell
Insert cell
stylesheet(Stylesheet)
Insert cell
Insert cell
Insert cell
Insert cell
Insert cell

Purpose-built for displays of data

Observable is your go-to platform for exploring data and creating expressive data visualizations. Use reactive JavaScript notebooks for prototyping and a collaborative canvas for visual data exploration and dashboard creation.
Learn more