scratch-vm/src/util/color.js

var Color = function () {};

/**
 * @typedef {object} RGBObject - An object representing a color in RGB format.
 * @property {number} r - the red component, in the range [0, 255].
 * @property {number} g - the green component, in the range [0, 255].
 * @property {number} b - the blue component, in the range [0, 255].
 */

/**
 * @typedef {object} HSVObject - An object representing a color in HSV format.
 * @property {number} h - hue, in the range [0-359).
 * @property {number} s - saturation, in the range [0,1].
 * @property {number} v - value, in the range [0,1].
 */

/** @type {RGBObject} */
Color.RGB_BLACK = {r: 0, g: 0, b: 0};

/** @type {RGBObject} */
Color.RGB_WHITE = {r: 255, g: 255, b: 255};

/**
 * Convert a Scratch decimal color to a hex string, #RRGGBB.
 * @param {number} decimal RGB color as a decimal.
 * @return {string} RGB color as #RRGGBB hex string.
 */
Color.decimalToHex = function (decimal) {
    if (decimal < 0) {
        decimal += 0xFFFFFF + 1;
    }
    var hex = Number(decimal).toString(16);
    hex = '#' + '000000'.substr(0, 6 - hex.length) + hex;
    return hex;
};

/**
 * Convert a Scratch decimal color to an RGB color object.
 * @param {number} decimal RGB color as decimal.
 * @returns {RGBObject} {r: R, g: G, b: B}, values between 0-255
 */
Color.decimalToRgb = function (decimal) {
    var r = (decimal >> 16) & 0xFF;
    var g = (decimal >> 8) & 0xFF;
    var b = decimal & 0xFF;
    return {r: r, g: g, b: b};
};

/**
 * Convert a hex color (e.g., F00, #03F, #0033FF) to an RGB color object.
 * CC-BY-SA Tim Down:
 * https://stackoverflow.com/questions/5623838/rgb-to-hex-and-hex-to-rgb
 * @param {!string} hex Hex representation of the color.
 * @return {Object} {r: R, g: G, b: B}, 0-255, or null.
 */
Color.hexToRgb = function (hex) {
    var shorthandRegex = /^#?([a-f\d])([a-f\d])([a-f\d])$/i;
    hex = hex.replace(shorthandRegex, function (m, r, g, b) {
        return r + r + g + g + b + b;
    });
    var result = /^#?([a-f\d]{2})([a-f\d]{2})([a-f\d]{2})$/i.exec(hex);
    return result ? {
        r: parseInt(result[1], 16),
        g: parseInt(result[2], 16),
        b: parseInt(result[3], 16)
    } : null;
};

/**
 * Convert an RGB color object to a hex color.
 * @param {Object} rgb {r: R, g: G, b: B}, values between 0-255.
 * @return {!string} Hex representation of the color.
 */
Color.rgbToHex = function (rgb) {
    return Color.decimalToHex(Color.rgbToDecimal(rgb));
};

/**
 * Convert an RGB color object to a Scratch decimal color.
 * @param {Object} rgb {r: R, g: G, b: B}, values between 0-255.
 * @return {!number} Number representing the color.
 */
Color.rgbToDecimal = function (rgb) {
    return (rgb.r << 16) + (rgb.g << 8) + rgb.b;
};

/**
* Convert a hex color (e.g., F00, #03F, #0033FF) to a decimal color number.
* @param {!string} hex Hex representation of the color.
* @return {!number} Number representing the color.
*/
Color.hexToDecimal = function (hex) {
    return Color.rgbToDecimal(Color.hexToRgb(hex));
};

/**
 * Convert an HSV color to RGB format.
 * @param {HSVObject} hsv - {h: hue [0,360), s: saturation [0,1], v: value [0,1]}
 * @returns {RGBObject} rgb - {r: red [0,255], g: green [0,255], b: blue [0,255]}.
 */
Color.hsvToRgb = function (hsv) {
    var h = hsv.h;
    var s = hsv.s;
    var v = hsv.v;

    h = h % 360;
    if (h < 0) h += 360;
    s = Math.max(0, Math.min(s, 1));
    v = Math.max(0, Math.min(v, 1));

    var i = Math.floor(h / 60);
    var f = (h / 60) - i;
    var p = v * (1 - s);
    var q = v * (1 - (s * f));
    var t = v * (1 - (s * (1 - f)));

    var r, g, b;
    if (i == 0) { r = v; g = t; b = p; }
    else if (i == 1) { r = q; g = v; b = p; }
    else if (i == 2) { r = p; g = v; b = t; }
    else if (i == 3) { r = p; g = q; b = v; }
    else if (i == 4) { r = t; g = p; b = v; }
    else if (i == 5) { r = v; g = p; b = q; }

    return {
        r: Math.floor(r * 255),
        g: Math.floor(g * 255),
        b: Math.floor(b * 255)
    };
};

/**
 * Convert an RGB color to HSV format.
 * @param {RGBObject} rgb - {r: red [0,255], g: green [0,255], b: blue [0,255]}.
 * @returns {HSVObject} hsv - {h: hue [0,360), s: saturation [0,1], v: value [0,1]}
 */
Color.rgbToHsv = function (rgb) {
    var v, x, f, i;
    var h = 0, s = 0;
    var r = rgb.r;
    var g = rgb.g;
    var b = rgb.b;
    x = Math.min(Math.min(r, g), b);
    v = Math.max(Math.max(r, g), b);

    // For grays, hue will be arbitrarily reported as zero. Otherwise, calculate
    if (x != v) {
        f = (r == x) ? g - b : ((g == x) ? b - r : r - g);
        i = (r == x) ? 3 : ((g == x) ? 5 : 1);
        h = ((i - (f / (v - x))) * 60) % 360;
        s = (v - x) / v;
    }

    return {h: h, s: s, v: v};
};

/**
 * Linear interpolation between rgb0 and rgb1.
 * @param {RGBObject} rgb0 - the color corresponding to fraction1 <= 0.
 * @param {RGBObject} rgb1 - the color corresponding to fraction1 >= 1.
 * @param {number} fraction1 - the interpolation parameter. If this is 0.5, for example, mix the two colors equally.
 * @returns {RGBObject} the interpolated color.
 */
Color.mixRgb = function (rgb0, rgb1, fraction1) {
    if (fraction1 <= 0) return rgb0;
    if (fraction1 >= 1) return rgb1;
    var fraction0 = 1 - fraction1;
    return {
        r: fraction0 * rgb0.r + fraction1 * rgb1.r,
        g: fraction0 * rgb0.g + fraction1 * rgb1.g,
        b: fraction0 * rgb0.b + fraction1 * rgb1.b
    };
};

module.exports = Color;