hsla.js

/*!
 * Stylus - HSLA
 * Copyright (c) Automattic <developer.wordpress.com>
 * MIT Licensed
 */

/**
 * Module dependencies.
 */

var Node = require('./node')
  , nodes = require('./');

/**
 * Initialize a new `HSLA` with the given h,s,l,a component values.
 *
 * @param {Number} h
 * @param {Number} s
 * @param {Number} l
 * @param {Number} a
 * @api public
 */

var HSLA = exports = module.exports = function HSLA(h,s,l,a){
  Node.call(this);
  this.h = clampDegrees(h);
  this.s = clampPercentage(s);
  this.l = clampPercentage(l);
  this.a = clampAlpha(a);
  this.hsla = this;
};

/**
 * Inherit from `Node.prototype`.
 */

HSLA.prototype.__proto__ = Node.prototype;

/**
 * Return hsla(n,n,n,n).
 *
 * @return {String}
 * @api public
 */

HSLA.prototype.toString = function(){
  return 'hsla('
    + this.h + ','
    + this.s.toFixed(0) + '%,'
    + this.l.toFixed(0) + '%,'
    + this.a + ')';
};

/**
 * Return a clone of this node.
 * 
 * @return {Node}
 * @api public
 */

HSLA.prototype.clone = function(parent){
  var clone = new HSLA(
      this.h
    , this.s
    , this.l
    , this.a);
  clone.lineno = this.lineno;
  clone.column = this.column;
  clone.filename = this.filename;
  return clone;
};

/**
 * Return a JSON representation of this node.
 *
 * @return {Object}
 * @api public
 */

HSLA.prototype.toJSON = function(){
  return {
    __type: 'HSLA',
    h: this.h,
    s: this.s,
    l: this.l,
    a: this.a,
    lineno: this.lineno,
    column: this.column,
    filename: this.filename
  };
};

/**
 * Return rgba `RGBA` representation.
 *
 * @return {RGBA}
 * @api public
 */

HSLA.prototype.__defineGetter__('rgba', function(){
  return nodes.RGBA.fromHSLA(this);
});

/**
 * Return hash.
 *
 * @return {String}
 * @api public
 */

HSLA.prototype.__defineGetter__('hash', function(){
  return this.rgba.toString();
});

/**
 * Add h,s,l to the current component values.
 *
 * @param {Number} h
 * @param {Number} s
 * @param {Number} l
 * @return {HSLA} new node
 * @api public
 */

HSLA.prototype.add = function(h,s,l){
  return new HSLA(
      this.h + h
    , this.s + s
    , this.l + l
    , this.a);
};

/**
 * Subtract h,s,l from the current component values.
 *
 * @param {Number} h
 * @param {Number} s
 * @param {Number} l
 * @return {HSLA} new node
 * @api public
 */

HSLA.prototype.sub = function(h,s,l){
  return this.add(-h, -s, -l);
};

/**
 * Operate on `right` with the given `op`.
 *
 * @param {String} op
 * @param {Node} right
 * @return {Node}
 * @api public
 */

HSLA.prototype.operate = function(op, right){
  switch (op) {
    case '==':
    case '!=':
    case '<=':
    case '>=':
    case '<':
    case '>':
    case 'is a':
    case '||':
    case '&&':
      return this.rgba.operate(op, right);
    default:
      return this.rgba.operate(op, right).hsla;
  }
};

/**
 * Return `HSLA` representation of the given `color`.
 *
 * @param {RGBA} color
 * @return {HSLA}
 * @api public
 */

exports.fromRGBA = function(rgba){
  var r = rgba.r / 255
    , g = rgba.g / 255
    , b = rgba.b / 255
    , a = rgba.a;

  var min = Math.min(r,g,b)
    , max = Math.max(r,g,b)
    , l = (max + min) / 2
    , d = max - min
    , h, s;

  switch (max) {
    case min: h = 0; break;
    case r: h = 60 * (g-b) / d; break;
    case g: h = 60 * (b-r) / d + 120; break;
    case b: h = 60 * (r-g) / d + 240; break;
  }

  if (max == min) {
    s = 0;
  } else if (l < .5) {
    s = d / (2 * l);
  } else {
    s = d / (2 - 2 * l);
  }

  h %= 360;
  s *= 100;
  l *= 100;

  return new HSLA(h,s,l,a);
};

/**
 * Adjust lightness by `percent`.
 *
 * @param {Number} percent
 * @return {HSLA} for chaining
 * @api public
 */

HSLA.prototype.adjustLightness = function(percent){
  this.l = clampPercentage(this.l + this.l * (percent / 100));
  return this;
};

/**
 * Adjust hue by `deg`.
 *
 * @param {Number} deg
 * @return {HSLA} for chaining
 * @api public
 */

HSLA.prototype.adjustHue = function(deg){
  this.h = clampDegrees(this.h + deg);
  return this;
};

/**
 * Clamp degree `n` >= 0 and <= 360.
 *
 * @param {Number} n
 * @return {Number}
 * @api private
 */

function clampDegrees(n) {
  n = n % 360;
  return n >= 0 ? n : 360 + n;
}

/**
 * Clamp percentage `n` >= 0 and <= 100.
 *
 * @param {Number} n
 * @return {Number}
 * @api private
 */

function clampPercentage(n) {
  return Math.max(0, Math.min(n, 100));
}

/**
 * Clamp alpha `n` >= 0 and <= 1.
 *
 * @param {Number} n
 * @return {Number}
 * @api private
 */

function clampAlpha(n) {
  return Math.max(0, Math.min(n, 1));
}