--- /dev/null
+"use strict";
+
+// these algorithms are sourced from https://drafts.csswg.org/css-color/#color-conversion-code
+
+function lin_sRGB(RGB) {
+ // convert an array of sRGB values in the range 0.0 - 1.0
+ // to linear light (un-companded) form.
+ // https://en.wikipedia.org/wiki/SRGB
+ return RGB.map(function(val) {
+ if (val < 0.04045) {
+ return val / 12.92;
+ }
+
+ return Math.pow((val + 0.055) / 1.055, 2.4);
+ });
+}
+
+function matrixMultiple3d(matrix, vector) {
+ return [
+ matrix[0][0] * vector[0] +
+ matrix[0][1] * vector[1] +
+ matrix[0][2] * vector[2],
+ matrix[1][0] * vector[0] +
+ matrix[1][1] * vector[1] +
+ matrix[1][2] * vector[2],
+ matrix[2][0] * vector[0] +
+ matrix[2][1] * vector[1] +
+ matrix[2][2] * vector[2]
+ ];
+}
+
+function srgb2xyz(srgb) {
+ return matrixMultiple3d(
+ [
+ [0.4124564, 0.3575761, 0.1804375],
+ [0.2126729, 0.7151522, 0.072175],
+ [0.0193339, 0.119192, 0.9503041]
+ ],
+ srgb
+ );
+}
+
+function chromaticAdaptationD65_D50(xyz) {
+ return matrixMultiple3d(
+ [
+ [1.0478112, 0.0228866, -0.050127],
+ [0.0295424, 0.9904844, -0.0170491],
+ [-0.0092345, 0.0150436, 0.7521316]
+ ],
+ xyz
+ );
+}
+
+function xyz2lab(xyzIn) {
+ // Assuming XYZ is relative to D50, convert to CIE Lab
+ // from CIE standard, which now defines these as a rational fraction
+ const ε = 216 / 24389; // 6^3/29^3
+ const κ = 24389 / 27; // 29^3/3^3
+ const white = [0.9642, 1.0, 0.8249]; // D50 reference white
+
+ // compute xyz, which is XYZ scaled relative to reference white
+ const xyz = xyzIn.map((value, i) => value / white[i]);
+
+ // now compute f
+ const f = xyz.map(
+ value => (value > ε ? Math.cbrt(value) : (κ * value + 16) / 116)
+ );
+
+ return [
+ 116 * f[1] - 16, // L
+ 500 * (f[0] - f[1]), // a
+ 200 * (f[1] - f[2]) // b
+ ];
+}
+
+function rgb2hsl(r, g, b) {
+ r /= 255;
+ g /= 255;
+ b /= 255;
+ let h, s, l;
+ const M = Math.max(r, g, b);
+ const m = Math.min(r, g, b);
+ const d = M - m;
+ if (d === 0) {
+ h = 0;
+ } else if (M === r) {
+ h = ((g - b) / d) % 6;
+ } else if (M === g) {
+ h = (b - r) / d + 2;
+ } else {
+ h = (r - g) / d + 4;
+ }
+
+ h *= 60;
+
+ if (h < 0) {
+ h += 360;
+ }
+
+ l = (M + m) / 2;
+
+ if (d === 0) {
+ s = 0;
+ } else {
+ s = d / (1 - Math.abs(2 * l - 1));
+ }
+
+ s *= 100;
+ l *= 100;
+
+ return [Math.round(h), Math.round(s), Math.round(l)];
+}
+
+function rgb2hwb(rgb_r, rgb_g, rgb_b) {
+ rgb_r /= 255;
+ rgb_g /= 255;
+ rgb_b /= 255;
+
+ const w = Math.min(rgb_r, rgb_g, rgb_b);
+ const v = Math.max(rgb_r, rgb_g, rgb_b);
+
+ const b = 1 - v;
+
+ if (v === w) {
+ return [0, Math.round(w * 100), Math.round(b * 100)];
+ }
+
+ const f =
+ rgb_r === w ? rgb_g - rgb_b : rgb_g === w ? rgb_b - rgb_r : rgb_r - rgb_g;
+ const i = rgb_r === w ? 3 : rgb_g === w ? 5 : 1;
+
+ return [
+ Math.round((i - f / (v - w)) / 6 * 360) % 360,
+ Math.round(w * 100),
+ Math.round(b * 100)
+ ];
+}
+
+function perc255(value) {
+ return Math.round(value * 100 / 255) + "%";
+}
+
+function generateColorFuncs(hexString) {
+ if (hexString.length !== 7) {
+ throw new Error(
+ "Invalid hex string color definition (" +
+ hexString +
+ ") - expected 6 character hex string"
+ );
+ }
+ const rgb = [0, 0, 0];
+ for (let i = 0; i < 3; i += 1) {
+ rgb[i] = parseInt(hexString.substr(2 * i + 1, 2), 16);
+ }
+ const hsl = rgb2hsl(rgb[0], rgb[1], rgb[2]);
+ const hwb = rgb2hwb(rgb[0], rgb[1], rgb[2]);
+ const func = [];
+ const rgbStr = rgb[0] + "," + rgb[1] + "," + rgb[2];
+ const rgbPercStr =
+ perc255(rgb[0]) + "," + perc255(rgb[1]) + "," + perc255(rgb[2]);
+ const hslStr = hsl[0] + "," + hsl[1] + "%," + hsl[2] + "%";
+ const hwbStr = hwb[0] + "," + hwb[1] + "%," + hwb[2] + "%";
+
+ // *very* convoluted process, just to be able to establish if the color
+ // is gray -- or not.
+ const linRgb = lin_sRGB([rgb[0] / 255, rgb[1] / 255, rgb[2] / 255]);
+ const xyz_d65 = srgb2xyz(linRgb);
+ const xyz_d50 = chromaticAdaptationD65_D50(xyz_d65);
+ const lab = xyz2lab(xyz_d50);
+
+ func.push("rgb(" + rgbStr + ")");
+ func.push("rgba(" + rgbStr + ",1)");
+ func.push("rgba(" + rgbStr + ",100%)");
+ func.push("rgb(" + rgbPercStr + ")");
+ func.push("rgba(" + rgbPercStr + ",1)");
+ func.push("rgba(" + rgbPercStr + ",100%)");
+ func.push("hsl(" + hslStr + ")");
+ func.push("hsla(" + hslStr + ",1)");
+ func.push("hsla(" + hslStr + ",100%)");
+ func.push("hwb(" + hwbStr + ")");
+ func.push("hwb(" + hwbStr + ",1)");
+ func.push("hwb(" + hwbStr + ",100%)");
+
+ // technically, this should be 0 - but then #808080 wouldn't even be gray
+ if (lab[1] * lab[1] < 0.01 && lab[2] * lab[2] < 0.01) {
+ // yay! gray!
+ const grayStr = Math.round(lab[0]);
+ func.push("gray(" + grayStr + ")");
+ func.push("gray(" + grayStr + ",1)");
+ func.push("gray(" + grayStr + ",100%)");
+ func.push("gray(" + grayStr + "%)");
+ func.push("gray(" + grayStr + "%,1)");
+ func.push("gray(" + grayStr + "%,100%)");
+ }
+ return func;
+}
+
+module.exports = generateColorFuncs;
projects / dotfiles / .git / blobdiff