source: node_modules/color-convert/conversions.js

/* MIT license */
/* eslint-disable no-mixed-operators */
const cssKeywords = require('color-name');

// NOTE: conversions should only return primitive values (i.e. arrays, or
//       values that give correct `typeof` results).
//       do not use box values types (i.e. Number(), String(), etc.)

const reverseKeywords = {};
for (const key of Object.keys(cssKeywords)) {
        reverseKeywords[cssKeywords[key]] = key;
}

const convert = {
        rgb: {channels: 3, labels: 'rgb'},
        hsl: {channels: 3, labels: 'hsl'},
        hsv: {channels: 3, labels: 'hsv'},
        hwb: {channels: 3, labels: 'hwb'},
        cmyk: {channels: 4, labels: 'cmyk'},
        xyz: {channels: 3, labels: 'xyz'},
        lab: {channels: 3, labels: 'lab'},
        lch: {channels: 3, labels: 'lch'},
        hex: {channels: 1, labels: ['hex']},
        keyword: {channels: 1, labels: ['keyword']},
        ansi16: {channels: 1, labels: ['ansi16']},
        ansi256: {channels: 1, labels: ['ansi256']},
        hcg: {channels: 3, labels: ['h', 'c', 'g']},
        apple: {channels: 3, labels: ['r16', 'g16', 'b16']},
        gray: {channels: 1, labels: ['gray']}
};

module.exports = convert;

// Hide .channels and .labels properties
for (const model of Object.keys(convert)) {
        if (!('channels' in convert[model])) {
                throw new Error('missing channels property: ' + model);
        }

        if (!('labels' in convert[model])) {
                throw new Error('missing channel labels property: ' + model);
        }

        if (convert[model].labels.length !== convert[model].channels) {
                throw new Error('channel and label counts mismatch: ' + model);
        }

        const {channels, labels} = convert[model];
        delete convert[model].channels;
        delete convert[model].labels;
        Object.defineProperty(convert[model], 'channels', {value: channels});
        Object.defineProperty(convert[model], 'labels', {value: labels});
}

convert.rgb.hsl = function (rgb) {
        const r = rgb[0] / 255;
        const g = rgb[1] / 255;
        const b = rgb[2] / 255;
        const min = Math.min(r, g, b);
        const max = Math.max(r, g, b);
        const delta = max - min;
        let h;
        let s;

        if (max === min) {
                h = 0;
        } else if (r === max) {
                h = (g - b) / delta;
        } else if (g === max) {
                h = 2 + (b - r) / delta;
        } else if (b === max) {
                h = 4 + (r - g) / delta;
        }

        h = Math.min(h * 60, 360);

        if (h < 0) {
                h += 360;
        }

        const l = (min + max) / 2;

        if (max === min) {
                s = 0;
        } else if (l <= 0.5) {
                s = delta / (max + min);
        } else {
                s = delta / (2 - max - min);
        }

        return [h, s * 100, l * 100];
};

convert.rgb.hsv = function (rgb) {
        let rdif;
        let gdif;
        let bdif;
        let h;
        let s;

        const r = rgb[0] / 255;
        const g = rgb[1] / 255;
        const b = rgb[2] / 255;
        const v = Math.max(r, g, b);
        const diff = v - Math.min(r, g, b);
        const diffc = function (c) {
                return (v - c) / 6 / diff + 1 / 2;
        };

        if (diff === 0) {
                h = 0;
                s = 0;
        } else {
                s = diff / v;
                rdif = diffc(r);
                gdif = diffc(g);
                bdif = diffc(b);

                if (r === v) {
                        h = bdif - gdif;
                } else if (g === v) {
                        h = (1 / 3) + rdif - bdif;
                } else if (b === v) {
                        h = (2 / 3) + gdif - rdif;
                }

                if (h < 0) {
                        h += 1;
                } else if (h > 1) {
                        h -= 1;
                }
        }

        return [
                h * 360,
                s * 100,
                v * 100
        ];
};

convert.rgb.hwb = function (rgb) {
        const r = rgb[0];
        const g = rgb[1];
        let b = rgb[2];
        const h = convert.rgb.hsl(rgb)[0];
        const w = 1 / 255 * Math.min(r, Math.min(g, b));

        b = 1 - 1 / 255 * Math.max(r, Math.max(g, b));

        return [h, w * 100, b * 100];
};

convert.rgb.cmyk = function (rgb) {
        const r = rgb[0] / 255;
        const g = rgb[1] / 255;
        const b = rgb[2] / 255;

        const k = Math.min(1 - r, 1 - g, 1 - b);
        const c = (1 - r - k) / (1 - k) || 0;
        const m = (1 - g - k) / (1 - k) || 0;
        const y = (1 - b - k) / (1 - k) || 0;

        return [c * 100, m * 100, y * 100, k * 100];
};

function comparativeDistance(x, y) {
        /*
                See https://en.m.wikipedia.org/wiki/Euclidean_distance#Squared_Euclidean_distance
        */
        return (
                ((x[0] - y[0]) ** 2) +
                ((x[1] - y[1]) ** 2) +
                ((x[2] - y[2]) ** 2)
        );
}

convert.rgb.keyword = function (rgb) {
        const reversed = reverseKeywords[rgb];
        if (reversed) {
                return reversed;
        }

        let currentClosestDistance = Infinity;
        let currentClosestKeyword;

        for (const keyword of Object.keys(cssKeywords)) {
                const value = cssKeywords[keyword];

                // Compute comparative distance
                const distance = comparativeDistance(rgb, value);

                // Check if its less, if so set as closest
                if (distance < currentClosestDistance) {
                        currentClosestDistance = distance;
                        currentClosestKeyword = keyword;
                }
        }

        return currentClosestKeyword;
};

convert.keyword.rgb = function (keyword) {
        return cssKeywords[keyword];
};

convert.rgb.xyz = function (rgb) {
        let r = rgb[0] / 255;
        let g = rgb[1] / 255;
        let b = rgb[2] / 255;

        // Assume sRGB
        r = r > 0.04045 ? (((r + 0.055) / 1.055) ** 2.4) : (r / 12.92);
        g = g > 0.04045 ? (((g + 0.055) / 1.055) ** 2.4) : (g / 12.92);
        b = b > 0.04045 ? (((b + 0.055) / 1.055) ** 2.4) : (b / 12.92);

        const x = (r * 0.4124) + (g * 0.3576) + (b * 0.1805);
        const y = (r * 0.2126) + (g * 0.7152) + (b * 0.0722);
        const z = (r * 0.0193) + (g * 0.1192) + (b * 0.9505);

        return [x * 100, y * 100, z * 100];
};

convert.rgb.lab = function (rgb) {
        const xyz = convert.rgb.xyz(rgb);
        let x = xyz[0];
        let y = xyz[1];
        let z = xyz[2];

        x /= 95.047;
        y /= 100;
        z /= 108.883;

        x = x > 0.008856 ? (x ** (1 / 3)) : (7.787 * x) + (16 / 116);
        y = y > 0.008856 ? (y ** (1 / 3)) : (7.787 * y) + (16 / 116);
        z = z > 0.008856 ? (z ** (1 / 3)) : (7.787 * z) + (16 / 116);

        const l = (116 * y) - 16;
        const a = 500 * (x - y);
        const b = 200 * (y - z);

        return [l, a, b];
};

convert.hsl.rgb = function (hsl) {
        const h = hsl[0] / 360;
        const s = hsl[1] / 100;
        const l = hsl[2] / 100;
        let t2;
        let t3;
        let val;

        if (s === 0) {
                val = l * 255;
                return [val, val, val];
        }

        if (l < 0.5) {
                t2 = l * (1 + s);
        } else {
                t2 = l + s - l * s;
        }

        const t1 = 2 * l - t2;

        const rgb = [0, 0, 0];
        for (let i = 0; i < 3; i++) {
                t3 = h + 1 / 3 * -(i - 1);
                if (t3 < 0) {
                        t3++;
                }

                if (t3 > 1) {
                        t3--;
                }

                if (6 * t3 < 1) {
                        val = t1 + (t2 - t1) * 6 * t3;
                } else if (2 * t3 < 1) {
                        val = t2;
                } else if (3 * t3 < 2) {
                        val = t1 + (t2 - t1) * (2 / 3 - t3) * 6;
                } else {
                        val = t1;
                }

                rgb[i] = val * 255;
        }

        return rgb;
};

convert.hsl.hsv = function (hsl) {
        const h = hsl[0];
        let s = hsl[1] / 100;
        let l = hsl[2] / 100;
        let smin = s;
        const lmin = Math.max(l, 0.01);

        l *= 2;
        s *= (l <= 1) ? l : 2 - l;
        smin *= lmin <= 1 ? lmin : 2 - lmin;
        const v = (l + s) / 2;
        const sv = l === 0 ? (2 * smin) / (lmin + smin) : (2 * s) / (l + s);

        return [h, sv * 100, v * 100];
};

convert.hsv.rgb = function (hsv) {
        const h = hsv[0] / 60;
        const s = hsv[1] / 100;
        let v = hsv[2] / 100;
        const hi = Math.floor(h) % 6;

        const f = h - Math.floor(h);
        const p = 255 * v * (1 - s);
        const q = 255 * v * (1 - (s * f));
        const t = 255 * v * (1 - (s * (1 - f)));
        v *= 255;

        switch (hi) {
                case 0:
                        return [v, t, p];
                case 1:
                        return [q, v, p];
                case 2:
                        return [p, v, t];
                case 3:
                        return [p, q, v];
                case 4:
                        return [t, p, v];
                case 5:
                        return [v, p, q];
        }
};

convert.hsv.hsl = function (hsv) {
        const h = hsv[0];
        const s = hsv[1] / 100;
        const v = hsv[2] / 100;
        const vmin = Math.max(v, 0.01);
        let sl;
        let l;

        l = (2 - s) * v;
        const lmin = (2 - s) * vmin;
        sl = s * vmin;
        sl /= (lmin <= 1) ? lmin : 2 - lmin;
        sl = sl || 0;
        l /= 2;

        return [h, sl * 100, l * 100];
};

// http://dev.w3.org/csswg/css-color/#hwb-to-rgb
convert.hwb.rgb = function (hwb) {
        const h = hwb[0] / 360;
        let wh = hwb[1] / 100;
        let bl = hwb[2] / 100;
        const ratio = wh + bl;
        let f;

        // Wh + bl cant be > 1
        if (ratio > 1) {
                wh /= ratio;
                bl /= ratio;
        }

        const i = Math.floor(6 * h);
        const v = 1 - bl;
        f = 6 * h - i;

        if ((i & 0x01) !== 0) {
                f = 1 - f;
        }

        const n = wh + f * (v - wh); // Linear interpolation

        let r;
        let g;
        let b;
        /* eslint-disable max-statements-per-line,no-multi-spaces */
        switch (i) {
                default:
                case 6:
                case 0: r = v;  g = n;  b = wh; break;
                case 1: r = n;  g = v;  b = wh; break;
                case 2: r = wh; g = v;  b = n; break;
                case 3: r = wh; g = n;  b = v; break;
                case 4: r = n;  g = wh; b = v; break;
                case 5: r = v;  g = wh; b = n; break;
        }
        /* eslint-enable max-statements-per-line,no-multi-spaces */

        return [r * 255, g * 255, b * 255];
};

convert.cmyk.rgb = function (cmyk) {
        const c = cmyk[0] / 100;
        const m = cmyk[1] / 100;
        const y = cmyk[2] / 100;
        const k = cmyk[3] / 100;

        const r = 1 - Math.min(1, c * (1 - k) + k);
        const g = 1 - Math.min(1, m * (1 - k) + k);
        const b = 1 - Math.min(1, y * (1 - k) + k);

        return [r * 255, g * 255, b * 255];
};

convert.xyz.rgb = function (xyz) {
        const x = xyz[0] / 100;
        const y = xyz[1] / 100;
        const z = xyz[2] / 100;
        let r;
        let g;
        let b;

        r = (x * 3.2406) + (y * -1.5372) + (z * -0.4986);
        g = (x * -0.9689) + (y * 1.8758) + (z * 0.0415);
        b = (x * 0.0557) + (y * -0.2040) + (z * 1.0570);

        // Assume sRGB
        r = r > 0.0031308
                ? ((1.055 * (r ** (1.0 / 2.4))) - 0.055)
                : r * 12.92;

        g = g > 0.0031308
                ? ((1.055 * (g ** (1.0 / 2.4))) - 0.055)
                : g * 12.92;

        b = b > 0.0031308
                ? ((1.055 * (b ** (1.0 / 2.4))) - 0.055)
                : b * 12.92;

        r = Math.min(Math.max(0, r), 1);
        g = Math.min(Math.max(0, g), 1);
        b = Math.min(Math.max(0, b), 1);

        return [r * 255, g * 255, b * 255];
};

convert.xyz.lab = function (xyz) {
        let x = xyz[0];
        let y = xyz[1];
        let z = xyz[2];

        x /= 95.047;
        y /= 100;
        z /= 108.883;

        x = x > 0.008856 ? (x ** (1 / 3)) : (7.787 * x) + (16 / 116);
        y = y > 0.008856 ? (y ** (1 / 3)) : (7.787 * y) + (16 / 116);
        z = z > 0.008856 ? (z ** (1 / 3)) : (7.787 * z) + (16 / 116);

        const l = (116 * y) - 16;
        const a = 500 * (x - y);
        const b = 200 * (y - z);

        return [l, a, b];
};

convert.lab.xyz = function (lab) {
        const l = lab[0];
        const a = lab[1];
        const b = lab[2];
        let x;
        let y;
        let z;

        y = (l + 16) / 116;
        x = a / 500 + y;
        z = y - b / 200;

        const y2 = y ** 3;
        const x2 = x ** 3;
        const z2 = z ** 3;
        y = y2 > 0.008856 ? y2 : (y - 16 / 116) / 7.787;
        x = x2 > 0.008856 ? x2 : (x - 16 / 116) / 7.787;
        z = z2 > 0.008856 ? z2 : (z - 16 / 116) / 7.787;

        x *= 95.047;
        y *= 100;
        z *= 108.883;

        return [x, y, z];
};

convert.lab.lch = function (lab) {
        const l = lab[0];
        const a = lab[1];
        const b = lab[2];
        let h;

        const hr = Math.atan2(b, a);
        h = hr * 360 / 2 / Math.PI;

        if (h < 0) {
                h += 360;
        }

        const c = Math.sqrt(a * a + b * b);

        return [l, c, h];
};

convert.lch.lab = function (lch) {
        const l = lch[0];
        const c = lch[1];
        const h = lch[2];

        const hr = h / 360 * 2 * Math.PI;
        const a = c * Math.cos(hr);
        const b = c * Math.sin(hr);

        return [l, a, b];
};

convert.rgb.ansi16 = function (args, saturation = null) {
        const [r, g, b] = args;
        let value = saturation === null ? convert.rgb.hsv(args)[2] : saturation; // Hsv -> ansi16 optimization

        value = Math.round(value / 50);

        if (value === 0) {
                return 30;
        }

        let ansi = 30
                + ((Math.round(b / 255) << 2)
                | (Math.round(g / 255) << 1)
                | Math.round(r / 255));

        if (value === 2) {
                ansi += 60;
        }

        return ansi;
};

convert.hsv.ansi16 = function (args) {
        // Optimization here; we already know the value and don't need to get
        // it converted for us.
        return convert.rgb.ansi16(convert.hsv.rgb(args), args[2]);
};

convert.rgb.ansi256 = function (args) {
        const r = args[0];
        const g = args[1];
        const b = args[2];

        // We use the extended greyscale palette here, with the exception of
        // black and white. normal palette only has 4 greyscale shades.
        if (r === g && g === b) {
                if (r < 8) {
                        return 16;
                }

                if (r > 248) {
                        return 231;
                }

                return Math.round(((r - 8) / 247) * 24) + 232;
        }

        const ansi = 16
                + (36 * Math.round(r / 255 * 5))
                + (6 * Math.round(g / 255 * 5))
                + Math.round(b / 255 * 5);

        return ansi;
};

convert.ansi16.rgb = function (args) {
        let color = args % 10;

        // Handle greyscale
        if (color === 0 || color === 7) {
                if (args > 50) {
                        color += 3.5;
                }

                color = color / 10.5 * 255;

                return [color, color, color];
        }

        const mult = (~~(args > 50) + 1) * 0.5;
        const r = ((color & 1) * mult) * 255;
        const g = (((color >> 1) & 1) * mult) * 255;
        const b = (((color >> 2) & 1) * mult) * 255;

        return [r, g, b];
};

convert.ansi256.rgb = function (args) {
        // Handle greyscale
        if (args >= 232) {
                const c = (args - 232) * 10 + 8;
                return [c, c, c];
        }

        args -= 16;

        let rem;
        const r = Math.floor(args / 36) / 5 * 255;
        const g = Math.floor((rem = args % 36) / 6) / 5 * 255;
        const b = (rem % 6) / 5 * 255;

        return [r, g, b];
};

convert.rgb.hex = function (args) {
        const integer = ((Math.round(args[0]) & 0xFF) << 16)
                + ((Math.round(args[1]) & 0xFF) << 8)
                + (Math.round(args[2]) & 0xFF);

        const string = integer.toString(16).toUpperCase();
        return '000000'.substring(string.length) + string;
};

convert.hex.rgb = function (args) {
        const match = args.toString(16).match(/[a-f0-9]{6}|[a-f0-9]{3}/i);
        if (!match) {
                return [0, 0, 0];
        }

        let colorString = match[0];

        if (match[0].length === 3) {
                colorString = colorString.split('').map(char => {
                        return char + char;
                }).join('');
        }

        const integer = parseInt(colorString, 16);
        const r = (integer >> 16) & 0xFF;
        const g = (integer >> 8) & 0xFF;
        const b = integer & 0xFF;

        return [r, g, b];
};

convert.rgb.hcg = function (rgb) {
        const r = rgb[0] / 255;
        const g = rgb[1] / 255;
        const b = rgb[2] / 255;
        const max = Math.max(Math.max(r, g), b);
        const min = Math.min(Math.min(r, g), b);
        const chroma = (max - min);
        let grayscale;
        let hue;

        if (chroma < 1) {
                grayscale = min / (1 - chroma);
        } else {
                grayscale = 0;
        }

        if (chroma <= 0) {
                hue = 0;
        } else
        if (max === r) {
                hue = ((g - b) / chroma) % 6;
        } else
        if (max === g) {
                hue = 2 + (b - r) / chroma;
        } else {
                hue = 4 + (r - g) / chroma;
        }

        hue /= 6;
        hue %= 1;

        return [hue * 360, chroma * 100, grayscale * 100];
};

convert.hsl.hcg = function (hsl) {
        const s = hsl[1] / 100;
        const l = hsl[2] / 100;

        const c = l < 0.5 ? (2.0 * s * l) : (2.0 * s * (1.0 - l));

        let f = 0;
        if (c < 1.0) {
                f = (l - 0.5 * c) / (1.0 - c);
        }

        return [hsl[0], c * 100, f * 100];
};

convert.hsv.hcg = function (hsv) {
        const s = hsv[1] / 100;
        const v = hsv[2] / 100;

        const c = s * v;
        let f = 0;

        if (c < 1.0) {
                f = (v - c) / (1 - c);
        }

        return [hsv[0], c * 100, f * 100];
};

convert.hcg.rgb = function (hcg) {
        const h = hcg[0] / 360;
        const c = hcg[1] / 100;
        const g = hcg[2] / 100;

        if (c === 0.0) {
                return [g * 255, g * 255, g * 255];
        }

        const pure = [0, 0, 0];
        const hi = (h % 1) * 6;
        const v = hi % 1;
        const w = 1 - v;
        let mg = 0;

        /* eslint-disable max-statements-per-line */
        switch (Math.floor(hi)) {
                case 0:
                        pure[0] = 1; pure[1] = v; pure[2] = 0; break;
                case 1:
                        pure[0] = w; pure[1] = 1; pure[2] = 0; break;
                case 2:
                        pure[0] = 0; pure[1] = 1; pure[2] = v; break;
                case 3:
                        pure[0] = 0; pure[1] = w; pure[2] = 1; break;
                case 4:
                        pure[0] = v; pure[1] = 0; pure[2] = 1; break;
                default:
                        pure[0] = 1; pure[1] = 0; pure[2] = w;
        }
        /* eslint-enable max-statements-per-line */

        mg = (1.0 - c) * g;

        return [
                (c * pure[0] + mg) * 255,
                (c * pure[1] + mg) * 255,
                (c * pure[2] + mg) * 255
        ];
};

convert.hcg.hsv = function (hcg) {
        const c = hcg[1] / 100;
        const g = hcg[2] / 100;

        const v = c + g * (1.0 - c);
        let f = 0;

        if (v > 0.0) {
                f = c / v;
        }

        return [hcg[0], f * 100, v * 100];
};

convert.hcg.hsl = function (hcg) {
        const c = hcg[1] / 100;
        const g = hcg[2] / 100;

        const l = g * (1.0 - c) + 0.5 * c;
        let s = 0;

        if (l > 0.0 && l < 0.5) {
                s = c / (2 * l);
        } else
        if (l >= 0.5 && l < 1.0) {
                s = c / (2 * (1 - l));
        }

        return [hcg[0], s * 100, l * 100];
};

convert.hcg.hwb = function (hcg) {
        const c = hcg[1] / 100;
        const g = hcg[2] / 100;
        const v = c + g * (1.0 - c);
        return [hcg[0], (v - c) * 100, (1 - v) * 100];
};

convert.hwb.hcg = function (hwb) {
        const w = hwb[1] / 100;
        const b = hwb[2] / 100;
        const v = 1 - b;
        const c = v - w;
        let g = 0;

        if (c < 1) {
                g = (v - c) / (1 - c);
        }

        return [hwb[0], c * 100, g * 100];
};

convert.apple.rgb = function (apple) {
        return [(apple[0] / 65535) * 255, (apple[1] / 65535) * 255, (apple[2] / 65535) * 255];
};

convert.rgb.apple = function (rgb) {
        return [(rgb[0] / 255) * 65535, (rgb[1] / 255) * 65535, (rgb[2] / 255) * 65535];
};

convert.gray.rgb = function (args) {
        return [args[0] / 100 * 255, args[0] / 100 * 255, args[0] / 100 * 255];
};

convert.gray.hsl = function (args) {
        return [0, 0, args[0]];
};

convert.gray.hsv = convert.gray.hsl;

convert.gray.hwb = function (gray) {
        return [0, 100, gray[0]];
};

convert.gray.cmyk = function (gray) {
        return [0, 0, 0, gray[0]];
};

convert.gray.lab = function (gray) {
        return [gray[0], 0, 0];
};

convert.gray.hex = function (gray) {
        const val = Math.round(gray[0] / 100 * 255) & 0xFF;
        const integer = (val << 16) + (val << 8) + val;

        const string = integer.toString(16).toUpperCase();
        return '000000'.substring(string.length) + string;
};

convert.rgb.gray = function (rgb) {
        const val = (rgb[0] + rgb[1] + rgb[2]) / 3;
        return [val / 255 * 100];
};