Visualization toolmaker. Founder @observablehq. Creator @d3. Former @nytgraphics. Pronounced BOSS-tock.
Published
Edited
Nov 27, 2019
2 forks
10 stars
ramp(t => bb(t * 20000 + 1000))
function bb_spectrum(v, T) {
return 2 * h * (v ** 3) / (c ** 2) / (Math.exp(h * v / (k * T)) - 1);
}
function bb_rgb(T) {
return xyz_rgb(normalize(spectrum_xyz(v => bb_spectrum(v, T))));
}
function bb(T) {
return `rgb(${bb_rgb(T).map(c => Math.round(c * 255))})`;
}
cmf = (await FileAttachment("cmf.csv").text())
.split(/,|\n/g)
.map(Number)
.filter((_, i) => i % 4)
function spectrum_xyz(spectrum) {
let X = 0, Y = 0, Z = 0;
for (let i = -1, lambda = 390; lambda <= 830; ++lambda) {
const v = c / (lambda * 1e-9);
const B = spectrum(v);
X += B * cmf[++i];
Y += B * cmf[++i];
Z += B * cmf[++i];
}
const K = X + Y + Z;
return [X / K, Y / K, Z / K];
}
function ramp(rgb, height = 66) {
const context = DOM.context2d(width, height, 1);
context.canvas.style.imageRendering = "pixelated";
for (let x = 0; x < width; ++x) {
context.fillStyle = rgb(x / (width - 1));
context.fillRect(x, 0, 1, height);
}
return context.canvas;
}
function normalize(color) {
const max = Math.max(...color);
return max > 0 ? color.map(c => c / max) : color;
}
function constrain(color) {
const min = -Math.min(0, ...color);
return min > 0 ? color.map(c => c + min) : color;
}
function xyz_rgb(xyz) {
return lrgb_rgb(matrix_multiply_vector(matrix_xyzd50_lrgb, xyz));
}
import {lrgb_rgb, matrix_xyzd65_lrgb, matrix_xyzd50_lrgb, matrix_multiply_vector} from "@mbostock/lab-and-rgb"
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