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base-color.js
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base-color.js
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// mkcolor - a vim color scheme randomizer/previewer
// Copyright (C) 2020 QuietMisdreavus
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU Affero General Public License as published
// by the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU Affero General Public License for more details.
// You should have received a copy of the GNU Affero General Public License
// along with this program. If not, see <https://www.gnu.org/licenses/>.
function clamp(val, min, max) {
if (val < min) {
return min;
} else if (val > max) {
return max;
} else {
return val;
}
}
// calculate the Relative Luminance of the given RGB color
function luminance(col) {
function lumVal(v) {
let frac = v / 255;
if (frac <= 0.03928) {
return frac / 12.92;
} else {
return Math.pow(((frac+0.055)/1.055), 2.4);
}
}
let rVal = lumVal(col.r);
let gVal = lumVal(col.g);
let bVal = lumVal(col.b);
return (rVal * 0.2126) + (gVal * 0.7152) + (bVal * 0.0722);
}
// calculate the Contrast Ratio of the given RGB colors
function contrastRatio(col1, col2) {
let lum1 = luminance(col1);
let lum2 = luminance(col2);
let darker = Math.min(lum1, lum2);
let lighter = Math.max(lum1, lum2);
return (lighter + 0.05) / (darker + 0.05);
}
function labDistance(col1, col2) {
return Math.hypot(col1.lab.l - col2.lab.l,
col1.lab.a - col2.lab.a,
col1.lab.b - col2.lab.b);
}
// returns a new RGB color using the given RGB values, and, if present, the given ANSI index
function newColor(r, g, b, idx, lab) {
let col = { r: r, g: g, b: b };
let rStr = col.r.toString(16).padStart(2, '0').toUpperCase();
let gStr = col.g.toString(16).padStart(2, '0').toUpperCase();
let bStr = col.b.toString(16).padStart(2, '0').toUpperCase();
col.hex = `#${rStr}${gStr}${bStr}`;
col.text = `#${rStr}${gStr}${bStr}`;
if (idx) {
col.idx = idx;
col.text += ` (ANSI ${idx})`;
}
col.hsv = hsvFromColor(col);
col.ish = col.hsv.ish;
if (lab) {
col.lab = lab;
} else {
col.lab = labFromColor(col);
}
return col;
}
function hsvFromColor(col) {
var max = Math.max(col.r, col.g, col.b);
var min = Math.min(col.r, col.g, col.b);
var d = max - min;
var s = (max === 0 ? 0 : d / max);
var v = max / 255;
var h;
switch (max) {
case min:
h = 0;
break;
case col.r:
h = (col.g - col.b) + d * (col.g < col.b ? 6 : 0);
h /= 6 * d;
break;
case col.g:
h = (col.b - col.r) + d * 2;
h /= 6 * d;
break;
case col.b:
h = (col.r - col.g) + d * 4;
h /= 6 * d;
break;
}
var ish;
if (s < 0.1) {
ish = "greyish";
} else if (v < 0.1) {
ish = "blackish";
} else {
if (h < 0.1) {
ish = "reddish";
} else if (h < 0.233) {
ish = "yellowish";
} else if (h < 0.433) {
ish = "greenish";
} else if (h < 0.566) {
ish = "cyanish";
} else if (h < 0.766) {
ish = "blueish";
} else if (h < 0.9) {
ish = "magentaish";
} else {
ish = "reddish";
}
}
return {
h: h,
s: s,
v: v,
ish: ish
};
}
// consts used in the CIELAB conversion
const sigma = (6 / 29);
const sigma2 = Math.pow(6 / 29, 2);
const sigma3 = Math.pow(6 / 29, 3);
// XXX: this function contains a matrix multiplication that i pulled out into slow math! i didn't
// necessarily care about speed here, just that i didn't want to pull in a dependency to do quick
// matrix math >_> (or to do the conversion for me, e.g. chroma-js)
function labFromColor(col) {
function xyzFromColor(col) {
// apply gamma-expansion
function gamma(u) {
if (u <= 0.04045) {
return u / 12.92;
} else {
let val = (u + 0.055) / 1.055;
return Math.pow(val, 2.4);
}
}
let r = gamma(col.r / 255);
let g = gamma(col.g / 255);
let b = gamma(col.b / 255);
return {
x: (0.42139080 * r) + (0.35758434 * g) + (0.18048079 * b),
y: (0.21263901 * r) + (0.71516868 * g) + (0.07219232 * b),
z: (0.01933082 * r) + (0.11919478 * g) + (0.95053215 * b)
};
}
function labFromXyz(xyz) {
function f(t) {
if (t > sigma3) {
return Math.pow(t, 1/3);
} else {
return (t / (3 * sigma2)) + (4 / 29);
}
}
let normX = f(xyz.x / 0.9505);
let normY = f(xyz.y);
let normZ = f(xyz.z / 1.0890);
return {
l: (116 * normY) - 16,
a: 500 * (normX - normY),
b: 200 * (normY - normZ)
};
}
return labFromXyz(xyzFromColor(col));
}
function colorFromLab(lab) {
function xyzFromLab(lab) {
function f(t) {
if (t > sigma) {
return Math.pow(t, 3);
} else {
return 3 * sigma2 * (t - (4/29));
}
}
let lTerm = (lab.l + 16) / 116;
return {
x: 0.9505 * f(lTerm + (lab.a / 500)),
y: f(lTerm),
z: 1.0890 * f(lTerm - (lab.b / 200))
};
}
function colorFromXyz(xyz) {
function gamma(u) {
if (u <= 0.0031308) {
return u * 12.92;
} else {
return (1.055 * Math.pow(u, (1 / 2.4))) - 0.055
}
}
let linearR = (xyz.x * 3.24096994) + (xyz.y * -1.53738318) + (xyz.z * -0.49861076);
let linearG = (xyz.x * -0.96924364) + (xyz.y * 1.87596750) + (xyz.z * 0.04155506);
let linearB = (xyz.x * 0.05563008) + (xyz.y * -0.20397696) + (xyz.z * 1.05697151);
let r = clamp(Math.round(gamma(linearR) * 255), 0, 255);
let g = clamp(Math.round(gamma(linearG) * 255), 0, 255);
let b = clamp(Math.round(gamma(linearB) * 255), 0, 255);
return newColor(r, g, b, undefined, lab);
}
return colorFromXyz(xyzFromLab(lab));
}
const crMidpoint = newColor(0xcf, 0x0d, 0xcc);