439 lines
12 KiB
JavaScript
439 lines
12 KiB
JavaScript
const tinycolor = require('tinycolor2');
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/**
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* @typedef {Object} TinyGradient.StopInput
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* @property {ColorInput} color
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* @property {number} pos
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*/
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/**
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* @typedef {Object} TinyGradient.StepValue
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* @type {number} [r]
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* @type {number} [g]
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* @type {number} [b]
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* @type {number} [h]
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* @type {number} [s]
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* @type {number} [v]
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* @type {number} [a]
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*/
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/**
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* @type {StepValue}
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*/
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const RGBA_MAX = { r: 256, g: 256, b: 256, a: 1 };
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/**
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* @type {StepValue}
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*/
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const HSVA_MAX = { h: 360, s: 1, v: 1, a: 1 };
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/**
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* Linearly compute the step size between start and end (not normalized)
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* @param {StepValue} start
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* @param {StepValue} end
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* @param {number} steps - number of desired steps
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* @return {StepValue}
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*/
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function stepize(start, end, steps) {
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let step = {};
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for (let k in start) {
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if (start.hasOwnProperty(k)) {
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step[k] = steps === 0 ? 0 : (end[k] - start[k]) / steps;
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}
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}
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return step;
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}
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/**
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* Compute the final step color
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* @param {StepValue} step - from `stepize`
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* @param {StepValue} start
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* @param {number} i - color index
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* @param {StepValue} max - rgba or hsva of maximum values for each channel
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* @return {StepValue}
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*/
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function interpolate(step, start, i, max) {
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let color = {};
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for (let k in start) {
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if (start.hasOwnProperty(k)) {
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color[k] = step[k] * i + start[k];
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color[k] = color[k] < 0 ? color[k] + max[k] : (max[k] !== 1 ? color[k] % max[k] : color[k]);
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}
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}
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return color;
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}
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/**
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* Generate gradient with RGBa interpolation
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* @param {StopInput} stop1
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* @param {StopInput} stop2
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* @param {number} steps
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* @return {tinycolor[]} color1 included, color2 excluded
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*/
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function interpolateRgb(stop1, stop2, steps) {
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const start = stop1.color.toRgb();
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const end = stop2.color.toRgb();
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const step = stepize(start, end, steps);
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let gradient = [stop1.color];
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for (let i = 1; i < steps; i++) {
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const color = interpolate(step, start, i, RGBA_MAX);
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gradient.push(tinycolor(color));
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}
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return gradient;
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}
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/**
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* Generate gradient with HSVa interpolation
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* @param {StopInput} stop1
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* @param {StopInput} stop2
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* @param {number} steps
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* @param {boolean|'long'|'short'} mode
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* @return {tinycolor[]} color1 included, color2 excluded
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*/
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function interpolateHsv(stop1, stop2, steps, mode) {
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const start = stop1.color.toHsv();
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const end = stop2.color.toHsv();
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// rgb interpolation if one of the steps in grayscale
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if (start.s === 0 || end.s === 0) {
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return interpolateRgb(stop1, stop2, steps);
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}
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let trigonometric;
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if (typeof mode === 'boolean') {
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trigonometric = mode;
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}
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else {
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const trigShortest = (start.h < end.h && end.h - start.h < 180) || (start.h > end.h && start.h - end.h > 180);
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trigonometric = (mode === 'long' && trigShortest) || (mode === 'short' && !trigShortest);
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}
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const step = stepize(start, end, steps);
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let gradient = [stop1.color];
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// recompute hue
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let diff;
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if ((start.h <= end.h && !trigonometric) || (start.h >= end.h && trigonometric)) {
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diff = end.h - start.h;
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}
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else if (trigonometric) {
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diff = 360 - end.h + start.h;
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}
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else {
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diff = 360 - start.h + end.h;
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}
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step.h = Math.pow(-1, trigonometric ? 1 : 0) * Math.abs(diff) / steps;
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for (let i = 1; i < steps; i++) {
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const color = interpolate(step, start, i, HSVA_MAX);
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gradient.push(tinycolor(color));
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}
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return gradient;
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}
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/**
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* Compute substeps between each stops
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* @param {StopInput[]} stops
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* @param {number} steps
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* @return {number[]}
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*/
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function computeSubsteps(stops, steps) {
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const l = stops.length;
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// validation
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steps = parseInt(steps, 10);
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if (isNaN(steps) || steps < 2) {
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throw new Error('Invalid number of steps (< 2)');
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}
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if (steps < l) {
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throw new Error('Number of steps cannot be inferior to number of stops');
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}
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// compute substeps from stop positions
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let substeps = [];
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for (let i = 1; i < l; i++) {
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const step = (steps - 1) * (stops[i].pos - stops[i - 1].pos);
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substeps.push(Math.max(1, Math.round(step)));
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}
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// adjust number of steps
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let totalSubsteps = 1;
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for (let n = l - 1; n--;) totalSubsteps += substeps[n];
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while (totalSubsteps !== steps) {
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if (totalSubsteps < steps) {
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const min = Math.min.apply(null, substeps);
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substeps[substeps.indexOf(min)]++;
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totalSubsteps++;
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}
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else {
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const max = Math.max.apply(null, substeps);
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substeps[substeps.indexOf(max)]--;
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totalSubsteps--;
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}
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}
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return substeps;
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}
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/**
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* Compute the color at a specific position
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* @param {StopInput[]} stops
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* @param {number} pos
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* @param {string} method
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* @param {StepValue} max
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* @returns {tinycolor}
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*/
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function computeAt(stops, pos, method, max) {
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if (pos < 0 || pos > 1) {
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throw new Error('Position must be between 0 and 1');
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}
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let start, end;
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for (let i = 0, l = stops.length; i < l - 1; i++) {
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if (pos >= stops[i].pos && pos < stops[i + 1].pos) {
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start = stops[i];
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end = stops[i + 1];
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break;
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}
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}
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if (!start) {
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start = end = stops[stops.length - 1];
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}
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const step = stepize(start.color[method](), end.color[method](), (end.pos - start.pos) * 100);
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const color = interpolate(step, start.color[method](), (pos - start.pos) * 100, max);
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return tinycolor(color);
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}
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class TinyGradient {
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/**
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* @param {StopInput[]|ColorInput[]} stops
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* @returns {TinyGradient}
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*/
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constructor(stops) {
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// validation
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if (stops.length < 2) {
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throw new Error('Invalid number of stops (< 2)');
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}
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const havingPositions = stops[0].pos !== undefined;
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let l = stops.length;
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let p = -1;
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let lastColorLess = false;
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// create tinycolor objects and clean positions
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this.stops = stops.map((stop, i) => {
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const hasPosition = stop.pos !== undefined;
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if (havingPositions ^ hasPosition) {
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throw new Error('Cannot mix positionned and not posionned color stops');
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}
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if (hasPosition) {
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const hasColor = stop.color !== undefined;
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if (!hasColor && (lastColorLess || i === 0 || i === l - 1)) {
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throw new Error('Cannot define two consecutive position-only stops');
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}
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lastColorLess = !hasColor;
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stop = {
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color : hasColor ? tinycolor(stop.color) : null,
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colorLess: !hasColor,
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pos : stop.pos
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};
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if (stop.pos < 0 || stop.pos > 1) {
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throw new Error('Color stops positions must be between 0 and 1');
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}
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else if (stop.pos < p) {
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throw new Error('Color stops positions are not ordered');
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}
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p = stop.pos;
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}
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else {
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stop = {
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color: tinycolor(stop.color !== undefined ? stop.color : stop),
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pos : i / (l - 1)
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};
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}
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return stop;
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});
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if (this.stops[0].pos !== 0) {
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this.stops.unshift({
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color: this.stops[0].color,
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pos : 0
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});
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l++;
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}
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if (this.stops[l - 1].pos !== 1) {
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this.stops.push({
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color: this.stops[l - 1].color,
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pos : 1
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});
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}
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}
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/**
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* Return new instance with reversed stops
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* @return {TinyGradient}
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*/
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reverse() {
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let stops = [];
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this.stops.forEach(function (stop) {
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stops.push({
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color: stop.color,
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pos : 1 - stop.pos
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});
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});
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return new TinyGradient(stops.reverse());
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}
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/**
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* Return new instance with looped stops
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* @return {TinyGradient}
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*/
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loop() {
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let stops1 = [];
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let stops2 = [];
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this.stops.forEach((stop) => {
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stops1.push({
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color: stop.color,
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pos : stop.pos / 2
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});
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});
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this.stops.slice(0, -1).forEach((stop) => {
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stops2.push({
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color: stop.color,
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pos : 1 - stop.pos / 2
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});
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});
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return new TinyGradient(stops1.concat(stops2.reverse()));
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}
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/**
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* Generate gradient with RGBa interpolation
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* @param {number} steps
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* @return {tinycolor[]}
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*/
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rgb(steps) {
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const substeps = computeSubsteps(this.stops, steps);
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let gradient = [];
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this.stops.forEach((stop, i) => {
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if (stop.colorLess) {
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stop.color = interpolateRgb(this.stops[i - 1], this.stops[i + 1], 2)[1];
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}
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});
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for (let i = 0, l = this.stops.length; i < l - 1; i++) {
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const rgb = interpolateRgb(this.stops[i], this.stops[i + 1], substeps[i]);
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gradient.splice(gradient.length, 0, ...rgb);
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}
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gradient.push(this.stops[this.stops.length - 1].color);
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return gradient;
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}
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/**
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* Generate gradient with HSVa interpolation
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* @param {number} steps
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* @param {boolean|'long'|'short'} [mode=false]
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* - false to step in clockwise
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* - true to step in trigonometric order
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* - 'short' to use the shortest way
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* - 'long' to use the longest way
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* @return {tinycolor[]}
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*/
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hsv(steps, mode) {
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const substeps = computeSubsteps(this.stops, steps);
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let gradient = [];
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this.stops.forEach((stop, i) => {
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if (stop.colorLess) {
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stop.color = interpolateHsv(this.stops[i - 1], this.stops[i + 1], 2, mode)[1];
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}
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});
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for (let i = 0, l = this.stops.length; i < l - 1; i++) {
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const hsv = interpolateHsv(this.stops[i], this.stops[i + 1], substeps[i], mode);
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gradient.splice(gradient.length, 0, ...hsv);
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}
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gradient.push(this.stops[this.stops.length - 1].color);
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return gradient;
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}
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/**
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* Generate CSS3 command (no prefix) for this gradient
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* @param {String} [mode=linear] - 'linear' or 'radial'
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* @param {String} [direction] - default is 'to right' or 'ellipse at center'
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* @return {String}
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*/
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css(mode, direction) {
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mode = mode || 'linear';
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direction = direction || (mode === 'linear' ? 'to right' : 'ellipse at center');
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let css = mode + '-gradient(' + direction;
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this.stops.forEach(function (stop) {
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css += ', ' + (stop.colorLess ? '' : stop.color.toRgbString() + ' ') + (stop.pos * 100) + '%';
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});
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css += ')';
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return css;
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}
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/**
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* Returns the color at specific position with RGBa interpolation
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* @param {number} pos, between 0 and 1
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* @return {tinycolor}
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*/
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rgbAt(pos) {
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return computeAt(this.stops, pos, 'toRgb', RGBA_MAX);
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}
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/**
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* Returns the color at specific position with HSVa interpolation
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* @param {number} pos, between 0 and 1
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* @return {tinycolor}
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*/
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hsvAt(pos) {
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return computeAt(this.stops, pos, 'toHsv', HSVA_MAX);
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}
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}
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/**
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* @param {StopInput[]|ColorInput[]|StopInput...|ColorInput...} stops
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* @returns {TinyGradient}
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*/
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module.exports = function (stops) {
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// varargs
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if (arguments.length === 1) {
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if (!Array.isArray(arguments[0])) {
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throw new Error('"stops" is not an array');
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}
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stops = arguments[0];
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}
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else {
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stops = Array.prototype.slice.call(arguments);
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}
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return new TinyGradient(stops);
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};
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