Visualization toolmaker. Founder @observablehq. Creator @d3. Former @nytgraphics. Pronounced BOSS-tock.
function rgb_jch(rgb) {
return cat02_jch(xyz_cat02(rgb_xyz(rgb)));
}
function jch_rgb(jch) {
return xyz_rgb(cat02_xyz(jch_cat02(jch)));
}
function rgb_xyz(rgb) {
return matrix_multiply_vector(matrix_lrgb_xyzd65, rgb_lrgb(rgb));
}
function xyz_rgb(xyz) {
return lrgb_rgb(matrix_multiply_vector(matrix_xyzd65_lrgb, xyz));
}
function xyz_cat02([x, y, z]) {
return [
( 0.7328 * x) + (0.4296 * y) - (0.1624 * z),
(-0.7036 * x) + (1.6975 * y) + (0.0061 * z),
( 0.0030 * x) + (0.0136 * y) + (0.9834 * z)
];
}
function cat02_xyz([l, m, s]) {
return [
( 1.096124 * l) - (0.278869 * m) + (0.182745 * s),
( 0.454369 * l) + (0.473533 * m) + (0.072098 * s),
(-0.009628 * l) - (0.005698 * m) + (1.015326 * s)
];
}
function cat02_hpe([l, m, s]) {
return [
( 0.7409792 * l) + (0.2180250 * m) + (0.0410058 * s),
( 0.2853532 * l) + (0.6242014 * m) + (0.0904454 * s),
(-0.0096280 * l) - (0.0056980 * m) + (1.0153260 * s)
];
}
function hpe_xyz([l, m, s]) {
return [
(1.910197 * l) - (1.112124 * m) + (0.201908 * s),
(0.370950 * l) + (0.629054 * m) - (0.000008 * s),
s
];
}
function aab_lms(A, aa, bb, nbb) {
const x = (A / nbb) + 0.305;
return [
(0.32787 * x) + (0.32145 * aa) + (0.20527 * bb),
(0.32787 * x) - (0.63507 * aa) - (0.18603 * bb),
(0.32787 * x) - (0.15681 * aa) - (4.49038 * bb)
];
}
function adapt(lms) {
return lms.map((c, i) => {
const p = Math.pow((CIECAM02_fl * c) / 100, 0.42);
return ((400 * p) / (27.13 + p)) + 0.1;
});
}
function invert_adapt(lms) {
return lms.map((c, i) => {
return (100 / CIECAM02_fl) * Math.pow((27.13 * Math.abs(c - 0.1)) / (400 - Math.abs(c - 0.1)), 1 / 0.42);
});
}
function transform(lms) {
return lms.map((c, i) => {
return c * (((D65_Y * CIECAM02_d) / D65_CAT02[i]) + (1 - CIECAM02_d));
});
}
function invert_transform(lms) {
return lms.map((c, i) => {
return c / (((D65_Y * CIECAM02_d) / D65_CAT02[i]) + (1 - CIECAM02_d));
});
}
function cat02_jch(lms) {
const lms_c = transform(lms);
const lms_p = cat02_hpe(lms_c);
const [lpa, mpa, spa] = adapt(lms_p);
const ca = lpa - ((12 * mpa) / 11) + (spa / 11);
const cb = (1 / 9) * (lpa + mpa - 2 * spa);
let h = (180 / Math.PI) * Math.atan2(cb, ca);
if (h < 0) h += 360;
const a = (2 * lpa + mpa + 0.05 * spa - 0.305 ) * CIECAM02_nbb;
const J = 100 * Math.pow(a / CIECAM02_aw, CIECAM02_c * CIECAM02_z);
const et = 0.25 * (Math.cos((h * Math.PI) / 180 + 2) + 3.8);
const t = ((50000 / 13) * CIECAM02_nc * CIECAM02_ncb * et * Math.sqrt(ca * ca + cb * cb)) / (lpa + mpa + (21 / 20) * spa);
const C = Math.pow(t, 0.9) * Math.sqrt(J / 100) * Math.pow(1.64 - Math.pow(0.29, CIECAM02_n), 0.73);
return [J, C, h];
}
function jch_cat02([J, C, h]) {
const t = Math.pow(C / (Math.sqrt(J / 100) * Math.pow(1.64 - Math.pow(0.29, CIECAM02_n), 0.73)), 1 / 0.9);
const et = 1 / 4 * (Math.cos(((h * Math.PI) / 180) + 2) + 3.8);
const a = Math.pow(J / 100, 1 / (CIECAM02_c * CIECAM02_z)) * CIECAM02_aw;
const p1 = ((50000 / 13) * CIECAM02_nc * CIECAM02_ncb) * et / t;
const p2 = (a / CIECAM02_nbb) + 0.305;
const p3 = 21 / 20;
let ca, cb;
const hr = (h * Math.PI) / 180;
const sr = Math.sin(hr);
const cr = Math.cos(hr);
if (Math.abs(sr) >= Math.abs(cr)) {
cb = (p2 * (2 + p3) * (460 / 1403)) / (p1 / sr + (2 + p3) * (220 / 1403) * (Math.cos(hr) / Math.sin(hr)) - (27 / 1403) + p3 * (6300 / 1403));
ca = cb * (Math.cos(hr) / Math.sin(hr));
} else {
ca = (p2 * (2 + p3) * (460 / 1403)) / (p1 / cr + (2 + p3) * (220 / 1403) - ((27 / 1403) - p3 * (6300 / 1403)) * (Math.sin(hr) / Math.cos(hr)));
cb = ca * (Math.sin(hr) / Math.cos(hr));
}
const lms_a = aab_lms(a, ca, cb, CIECAM02_nbb);
const lms_p = invert_adapt(lms_a);
const txyz = hpe_xyz(lms_p);
const lms_c = xyz_cat02(txyz);
return invert_transform(lms_c);
}
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