text: // Copyright 2006 The Closure Library Authors. All Rights Reserved.
  //
  // Licensed under the Apache License, Version 2.0 (the "License");
  // you may not use this file except in compliance with the License.
  // You may obtain a copy of the License at
  //
  //      http://www.apache.org/licenses/LICENSE-2.0
  //
  // Unless required by applicable law or agreed to in writing, software
  // distributed under the License is distributed on an "AS-IS" BASIS,
  // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  // See the License for the specific language governing permissions and
  // limitations under the License.
  
  /**
   * @fileoverview Utilities related to alpha/transparent colors and alpha color
   * conversion.
   */
  
  goog.provide('goog.color.alpha');
  
  goog.require('goog.color');
  
  
  /**
   * Parses an alpha color out of a string.
   * @param {string} str Color in some format.
   * @return {Object} Contains two properties: 'hex', which is a string containing
   *     a hex representation of the color, as well as 'type', which is a string
   *     containing the type of color format passed in ('hex', 'rgb', 'named').
   */
  goog.color.alpha.parse = function(str) {
    var result = {};
    str = String(str);
  
    var maybeHex = goog.color.prependHashIfNecessaryHelper(str);
    if (goog.color.alpha.isValidAlphaHexColor_(maybeHex)) {
      result.hex = goog.color.alpha.normalizeAlphaHex_(maybeHex);
      result.type = 'hex';
      return result;
    } else {
      var rgba = goog.color.alpha.isValidRgbaColor_(str);
      if (rgba.length) {
        result.hex = goog.color.alpha.rgbaArrayToHex(rgba);
        result.type = 'rgba';
        return result;
      } else {
        var hsla = goog.color.alpha.isValidHslaColor_(str);
        if (hsla.length) {
          result.hex = goog.color.alpha.hslaArrayToHex(hsla);
          result.type = 'hsla';
          return result;
        }
      }
    }
    throw Error(str + ' is not a valid color string');
  };
  
  
  /**
   * Converts a hex representation of a color to RGBA.
   * @param {string} hexColor Color to convert.
   * @return {string} string of the form 'rgba(R,G,B,A)' which can be used in
   *    styles.
   */
  goog.color.alpha.hexToRgbaStyle = function(hexColor) {
    return goog.color.alpha.rgbaStyle_(goog.color.alpha.hexToRgba(hexColor));
  };
  
  
  /**
   * Gets the hex color part of an alpha hex color. For example, from '#abcdef55'
   * return '#abcdef'.
   * @param {string} colorWithAlpha The alpha hex color to get the hex color from.
   * @return {string} The hex color where the alpha part has been stripped off.
   */
  goog.color.alpha.extractHexColor = function(colorWithAlpha) {
    if (goog.color.alpha.isValidAlphaHexColor_(colorWithAlpha)) {
      var fullColor = goog.color.prependHashIfNecessaryHelper(colorWithAlpha);
      var normalizedColor = goog.color.alpha.normalizeAlphaHex_(fullColor);
      return normalizedColor.substring(0, 7);
    } else {
      throw Error(colorWithAlpha + ' is not a valid 8-hex color string');
    }
  };
  
  
  /**
   * Gets the alpha color part of an alpha hex color. For example, from
   * '#abcdef55' return '55'. The result is guaranteed to be two characters long.
   * @param {string} colorWithAlpha The alpha hex color to get the hex color from.
   * @return {string} The hex color where the alpha part has been stripped off.
   */
  goog.color.alpha.extractAlpha = function(colorWithAlpha) {
    if (goog.color.alpha.isValidAlphaHexColor_(colorWithAlpha)) {
      var fullColor = goog.color.prependHashIfNecessaryHelper(colorWithAlpha);
      var normalizedColor = goog.color.alpha.normalizeAlphaHex_(fullColor);
      return normalizedColor.substring(7, 9);
    } else {
      throw Error(colorWithAlpha + ' is not a valid 8-hex color string');
    }
  };
  
  
  /**
   * Regular expression for extracting the digits in a hex color quadruplet.
   * @type {RegExp}
   * @private
   */
  goog.color.alpha.hexQuadrupletRe_ = /#(.)(.)(.)(.)/;
  
  
  /**
   * Normalize a hex representation of an alpha color.
   * @param {string} hexColor an alpha hex color string.
   * @return {string} hex color in the format '#rrggbbaa' with all lowercase
   *     literals.
   * @private
   */
  goog.color.alpha.normalizeAlphaHex_ = function(hexColor) {
    if (!goog.color.alpha.isValidAlphaHexColor_(hexColor)) {
      throw Error("'" + hexColor + "' is not a valid alpha hex color");
    }
    if (hexColor.length == 5) { // of the form #RGBA
      hexColor = hexColor.replace(goog.color.alpha.hexQuadrupletRe_,
          '#$1$1$2$2$3$3$4$4');
    }
    return hexColor.toLowerCase();
  };
  
  
  /**
   * Converts an 8-hex representation of a color to RGBA.
   * @param {string} hexColor Color to convert.
   * @return {Array} array containing [r, g, b] as ints in [0, 255].
   */
  goog.color.alpha.hexToRgba = function(hexColor) {
    // TODO(user): Enhance code sharing with goog.color, for example by
    //     adding a goog.color.genericHexToRgb method.
    hexColor = goog.color.alpha.normalizeAlphaHex_(hexColor);
    var r = parseInt(hexColor.substr(1, 2), 16);
    var g = parseInt(hexColor.substr(3, 2), 16);
    var b = parseInt(hexColor.substr(5, 2), 16);
    var a = parseInt(hexColor.substr(7, 2), 16);
  
    return [r, g, b, a / 255];
  };
  
  
  /**
   * Converts a color from RGBA to hex representation.
   * @param {number} r Amount of red, int between 0 and 255.
   * @param {number} g Amount of green, int between 0 and 255.
   * @param {number} b Amount of blue, int between 0 and 255.
   * @param {number} a Amount of alpha, float between 0 and 1.
   * @return {string} hex representation of the color.
   */
  goog.color.alpha.rgbaToHex = function(r, g, b, a) {
    var intAlpha = Math.floor(a * 255);
    if (isNaN(intAlpha) || intAlpha < 0 || intAlpha > 255) {
      // TODO(user): The CSS spec says the value should be clamped.
      throw Error('"(' + r + ',' + g + ',' + b + ',' + a +
          '") is not a valid RGBA color');
    }
    var hexA = goog.color.prependZeroIfNecessaryHelper(intAlpha.toString(16));
    return goog.color.rgbToHex(r, g, b) + hexA;
  };
  
  
  /**
   * Converts a color from HSLA to hex representation.
   * @param {number} h Amount of hue, int between 0 and 360.
   * @param {number} s Amount of saturation, int between 0 and 100.
   * @param {number} l Amount of lightness, int between 0 and 100.
   * @param {number} a Amount of alpha, float between 0 and 1.
   * @return {string} hex representation of the color.
   */
  goog.color.alpha.hslaToHex = function(h, s, l, a) {
    var intAlpha = Math.floor(a * 255);
    if (isNaN(intAlpha) || intAlpha < 0 || intAlpha > 255) {
      // TODO(user): The CSS spec says the value should be clamped.
      throw Error('"(' + h + ',' + s + ',' + l + ',' + a +
          '") is not a valid HSLA color');
    }
    var hexA = goog.color.prependZeroIfNecessaryHelper(intAlpha.toString(16));
    return goog.color.hslToHex(h, s / 100, l / 100) + hexA;
  };
  
  
  /**
   * Converts a color from RGBA to hex representation.
   * @param {Array.<number>} rgba Array of [r, g, b, a], with r, g, b in [0, 255]
   *     and a in [0, 1].
   * @return {string} hex representation of the color.
   */
  goog.color.alpha.rgbaArrayToHex = function(rgba) {
    return goog.color.alpha.rgbaToHex(rgba[0], rgba[1], rgba[2], rgba[3]);
  };
  
  
  /**
   * Converts a color from RGBA to an RGBA style string.
   * @param {number} r Value of red, in [0, 255].
   * @param {number} g Value of green, in [0, 255].
   * @param {number} b Value of blue, in [0, 255].
   * @param {number} a Value of alpha, in [0, 1].
   * @return {string} An 'rgba(r,g,b,a)' string ready for use in a CSS rule.
   */
  goog.color.alpha.rgbaToRgbaStyle = function(r, g, b, a) {
    if (isNaN(r) || r < 0 || r > 255 ||
        isNaN(g) || g < 0 || g > 255 ||
        isNaN(b) || b < 0 || b > 255 ||
        isNaN(a) || a < 0 || a > 1) {
      throw Error('"(' + r + ',' + g + ',' + b + ',' + a +
          ')" is not a valid RGBA color');
    }
    return goog.color.alpha.rgbaStyle_([r, g, b, a]);
  };
  
  
  /**
   * Converts a color from RGBA to an RGBA style string.
   * @param {(Array.<number>|Float32Array)} rgba Array of [r, g, b, a],
   *     with r, g, b in [0, 255] and a in [0, 1].
   * @return {string} An 'rgba(r,g,b,a)' string ready for use in a CSS rule.
   */
  goog.color.alpha.rgbaArrayToRgbaStyle = function(rgba) {
    return goog.color.alpha.rgbaToRgbaStyle(rgba[0], rgba[1], rgba[2], rgba[3]);
  };
  
  
  /**
   * Converts a color from HSLA to hex representation.
   * @param {Array.<number>} hsla Array of [h, s, l, a], where h is an integer in
   *     [0, 360], s and l are integers in [0, 100], and a is in [0, 1].
   * @return {string} hex representation of the color, such as '#af457eff'.
   */
  goog.color.alpha.hslaArrayToHex = function(hsla) {
    return goog.color.alpha.hslaToHex(hsla[0], hsla[1], hsla[2], hsla[3]);
  };
  
  
  /**
   * Converts a color from HSLA to an RGBA style string.
   * @param {Array.<number>} hsla Array of [h, s, l, a], where h is and integer in
   *     [0, 360], s and l are integers in [0, 100], and a is in [0, 1].
   * @return {string} An 'rgba(r,g,b,a)' string ready for use in a CSS rule.
   */
  goog.color.alpha.hslaArrayToRgbaStyle = function(hsla) {
    return goog.color.alpha.hslaToRgbaStyle(hsla[0], hsla[1], hsla[2], hsla[3]);
  };
  
  
  /**
   * Converts a color from HSLA to an RGBA style string.
   * @param {number} h Amount of hue, int between 0 and 360.
   * @param {number} s Amount of saturation, int between 0 and 100.
   * @param {number} l Amount of lightness, int between 0 and 100.
   * @param {number} a Amount of alpha, float between 0 and 1.
   * @return {string} An 'rgba(r,g,b,a)' string ready for use in a CSS rule.
   *     styles.
   */
  goog.color.alpha.hslaToRgbaStyle = function(h, s, l, a) {
    return goog.color.alpha.rgbaStyle_(goog.color.alpha.hslaToRgba(h, s, l, a));
  };
  
  
  /**
   * Converts a color from HSLA color space to RGBA color space.
   * @param {number} h Amount of hue, int between 0 and 360.
   * @param {number} s Amount of saturation, int between 0 and 100.
   * @param {number} l Amount of lightness, int between 0 and 100.
   * @param {number} a Amount of alpha, float between 0 and 1.
   * @return {Array.<number>} [r, g, b, a] values for the color, where r, g, b
   *     are integers in [0, 255] and a is a float in [0, 1].
   */
  goog.color.alpha.hslaToRgba = function(h, s, l, a) {
    return goog.color.hslToRgb(h, s / 100, l / 100).concat(a);
  };
  
  
  /**
   * Converts a color from RGBA color space to HSLA color space.
   * Modified from {@link http://en.wikipedia.org/wiki/HLS_color_space}.
   * @param {number} r Value of red, in [0, 255].
   * @param {number} g Value of green, in [0, 255].
   * @param {number} b Value of blue, in [0, 255].
   * @param {number} a Value of alpha, in [0, 255].
   * @return {Array.<number>} [h, s, l, a] values for the color, with h an int in
   *     [0, 360] and s, l and a in [0, 1].
   */
  goog.color.alpha.rgbaToHsla = function(r, g, b, a) {
    return goog.color.rgbToHsl(r, g, b).concat(a);
  };
  
  
  /**
   * Converts a color from RGBA color space to HSLA color space.
   * @param {Array.<number>} rgba [r, g, b, a] values for the color, each in
   *     [0, 255].
   * @return {Array.<number>} [h, s, l, a] values for the color, with h in
   *     [0, 360] and s, l and a in [0, 1].
   */
  goog.color.alpha.rgbaArrayToHsla = function(rgba) {
    return goog.color.alpha.rgbaToHsla(rgba[0], rgba[1], rgba[2], rgba[3]);
  };
  
  
  /**
   * Helper for isValidAlphaHexColor_.
   * @type {RegExp}
   * @private
   */
  goog.color.alpha.validAlphaHexColorRe_ = /^#(?:[0-9a-f]{4}){1,2}$/i;
  
  
  /**
   * Checks if a string is a valid alpha hex color.  We expect strings of the
   * format #RRGGBBAA (ex: #1b3d5f5b) or #RGBA (ex: #3CAF == #33CCAAFF).
   * @param {string} str String to check.
   * @return {boolean} Whether the string is a valid alpha hex color.
   * @private
   */
  // TODO(user): Support percentages when goog.color also supports them.
  goog.color.alpha.isValidAlphaHexColor_ = function(str) {
    return goog.color.alpha.validAlphaHexColorRe_.test(str);
  };
  
  
  /**
   * Helper for isNormalizedAlphaHexColor_.
   * @type {RegExp}
   * @private
   */
  goog.color.alpha.normalizedAlphaHexColorRe_ = /^#[0-9a-f]{8}$/;
  
  
  /**
   * Checks if a string is a normalized alpha hex color.
   * We expect strings of the format #RRGGBBAA (ex: #1b3d5f5b)
   * using only lowercase letters.
   * @param {string} str String to check.
   * @return {boolean} Whether the string is a normalized hex color.
   * @private
   */
  goog.color.alpha.isNormalizedAlphaHexColor_ = function(str) {
    return goog.color.alpha.normalizedAlphaHexColorRe_.test(str);
  };
  
  
  /**
   * Regular expression for matching and capturing RGBA style strings. Helper for
   * isValidRgbaColor_.
   * @type {RegExp}
   * @private
   */
  goog.color.alpha.rgbaColorRe_ =
      /^(?:rgba)?\((0|[1-9]\d{0,2}),\s?(0|[1-9]\d{0,2}),\s?(0|[1-9]\d{0,2}),\s?(0|1|0\.\d{0,10})\)$/i;
  
  
  /**
   * Regular expression for matching and capturing HSLA style strings. Helper for
   * isValidHslaColor_.
   * @type {RegExp}
   * @private
   */
  goog.color.alpha.hslaColorRe_ =
      /^(?:hsla)\((0|[1-9]\d{0,2}),\s?(0|[1-9]\d{0,2})\%,\s?(0|[1-9]\d{0,2})\%,\s?(0|1|0\.\d{0,10})\)$/i;
  
  
  /**
   * Checks if a string is a valid rgba color.  We expect strings of the format
   * '(r, g, b, a)', or 'rgba(r, g, b, a)', where r, g, b are ints in [0, 255]
   *     and a is a float in [0, 1].
   * @param {string} str String to check.
   * @return {Array.<number>} the integers [r, g, b, a] for valid colors or the
   *     empty array for invalid colors.
   * @private
   */
  goog.color.alpha.isValidRgbaColor_ = function(str) {
    // Each component is separate (rather than using a repeater) so we can
    // capture the match. Also, we explicitly set each component to be either 0,
    // or start with a non-zero, to prevent octal numbers from slipping through.
    var regExpResultArray = str.match(goog.color.alpha.rgbaColorRe_);
    if (regExpResultArray) {
      var r = Number(regExpResultArray[1]);
      var g = Number(regExpResultArray[2]);
      var b = Number(regExpResultArray[3]);
      var a = Number(regExpResultArray[4]);
      if (r >= 0 && r <= 255 &&
          g >= 0 && g <= 255 &&
          b >= 0 && b <= 255 &&
          a >= 0 && a <= 1) {
        return [r, g, b, a];
      }
    }
    return [];
  };
  
  
  /**
   * Checks if a string is a valid hsla color.  We expect strings of the format
   * 'hsla(h, s, l, a)', where s in an int in [0, 360], s and l are percentages
   *     between 0 and 100 such as '50%' or '70%', and a is a float in [0, 1].
   * @param {string} str String to check.
   * @return {Array.<number>} the integers [h, s, l, a] for valid colors or the
   *     empty array for invalid colors.
   * @private
   */
  goog.color.alpha.isValidHslaColor_ = function(str) {
    // Each component is separate (rather than using a repeater) so we can
    // capture the match. Also, we explicitly set each component to be either 0,
    // or start with a non-zero, to prevent octal numbers from slipping through.
    var regExpResultArray = str.match(goog.color.alpha.hslaColorRe_);
    if (regExpResultArray) {
      var h = Number(regExpResultArray[1]);
      var s = Number(regExpResultArray[2]);
      var l = Number(regExpResultArray[3]);
      var a = Number(regExpResultArray[4]);
      if (h >= 0 && h <= 360 &&
          s >= 0 && s <= 100 &&
          l >= 0 && l <= 100 &&
          a >= 0 && a <= 1) {
        return [h, s, l, a];
      }
    }
    return [];
  };
  
  
  /**
   * Takes an array of [r, g, b, a] and converts it into a string appropriate for
   * CSS styles. The alpha channel value is rounded to 3 decimal places to make
   * sure the produced string is not too long.
   * @param {Array.<number>} rgba [r, g, b, a] with r, g, b in [0, 255] and a
   *     in [0, 1].
   * @return {string} string of the form 'rgba(r,g,b,a)'.
   * @private
   */
  goog.color.alpha.rgbaStyle_ = function(rgba) {
    var roundedRgba = rgba.slice(0);
    roundedRgba[3] = Math.round(rgba[3] * 1000) / 1000;
    return 'rgba(' + roundedRgba.join(',') + ')';
  };
  
  
  /**
   * Converts from h,s,v,a values to a hex string
   * @param {number} h Hue, in [0, 1].
   * @param {number} s Saturation, in [0, 1].
   * @param {number} v Value, in [0, 255].
   * @param {number} a Alpha, in [0, 1].
   * @return {string} hex representation of the color.
   */
  goog.color.alpha.hsvaToHex = function(h, s, v, a) {
    var alpha = Math.floor(a * 255);
    return goog.color.hsvArrayToHex([h, s, v]) +
           goog.color.prependZeroIfNecessaryHelper(alpha.toString(16));
  };
  
  
  /**
   * Converts from an HSVA array to a hex string
   * @param {Array} hsva Array of [h, s, v, a] in
   *     [[0, 1], [0, 1], [0, 255], [0, 1]].
   * @return {string} hex representation of the color.
   */
  goog.color.alpha.hsvaArrayToHex = function(hsva) {
    return goog.color.alpha.hsvaToHex(hsva[0], hsva[1], hsva[2], hsva[3]);
  };
  