/* -*- Mode: Java; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set shiftwidth=2 tabstop=2 autoindent cindent expandtab: */
/* Copyright 2012 Mozilla Foundation
 *
 * 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.
 */
/* globals error, info, input, isArray, isDict, isName, isStream, isString,
           PDFFunction, warn */

'use strict';

var ColorSpace = (function ColorSpaceClosure() {
  // Constructor should define this.numComps, this.defaultColor, this.name
  function ColorSpace() {
    error('should not call ColorSpace constructor');
  }

  ColorSpace.prototype = {
    /**
     * Converts the color value to the RGB color. The color components are
     * located in the src array starting from the srcOffset. Returns the array
     * of the rgb components, each value ranging from [0,255].
     */
    getRgb: function ColorSpace_getRgb(src, srcOffset) {
      error('Should not call ColorSpace.getRgb');
    },
    /**
     * Converts the color value to the RGB color, similar to the getRgb method.
     * The result placed into the dest array starting from the destOffset.
     */
    getRgbItem: function ColorSpace_getRgb(src, srcOffset, dest, destOffset) {
      error('Should not call ColorSpace.getRgbItem');
    },
    /**
     * Converts the specified number of the color values to the RGB colors.
     * The colors are located in the src array starting from the srcOffset.
     * The result is placed into the dest array starting from the destOffset.
     * The src array items shall be in [0,2^bits) range, the dest array items
     * will be in [0,255] range.
     */
    getRgbBuffer: function ColorSpace_getRgbBuffer(src, srcOffset, count,
                                                   dest, destOffset, bits) {
      error('Should not call ColorSpace.getRgbBuffer');
    },
    /**
     * Determines amount of the bytes is required to store the reslut of the
     * conversion that done by the getRgbBuffer method.
     */
    getOutputLength: function ColorSpace_getOutputLength(inputLength) {
      error('Should not call ColorSpace.getOutputLength');
    },
    /**
     * Returns true if source data will be equal the result/output data.
     */
    isPassthrough: function ColorSpace_isPassthrough(bits) {
      return false;
    },
    /**
     * Creates the output buffer and converts the specified number of the color
     * values to the RGB colors, similar to the getRgbBuffer.
     */
    createRgbBuffer: function ColorSpace_createRgbBuffer(src, srcOffset,
                                                         count, bits) {
      if (this.isPassthrough(bits)) {
        return src.subarray(srcOffset);
      }
      var dest = new Uint8Array(count * 3);
      var numComponentColors = 1 << bits;
      // Optimization: create a color map when there is just one component and
      // we are converting more colors than the size of the color map. We
      // don't build the map if the colorspace is gray or rgb since those
      // methods are faster than building a map. This mainly offers big speed
      // ups for indexed and alternate colorspaces.
      if (this.numComps === 1 && count > numComponentColors &&
          this.name !== 'DeviceGray' && this.name !== 'DeviceRGB') {
        // TODO it may be worth while to cache the color map. While running
        // testing I never hit a cache so I will leave that out for now (perhaps
        // we are reparsing colorspaces too much?).
        var allColors = bits <= 8 ? new Uint8Array(numComponentColors) :
                                    new Uint16Array(numComponentColors);
        for (var i = 0; i < numComponentColors; i++) {
          allColors[i] = i;
        }
        var colorMap = new Uint8Array(numComponentColors * 3);
        this.getRgbBuffer(allColors, 0, numComponentColors, colorMap, 0, bits);

        var destOffset = 0;
        for (var i = 0; i < count; ++i) {
          var key = src[srcOffset++] * 3;
          dest[destOffset++] = colorMap[key];
          dest[destOffset++] = colorMap[key + 1];
          dest[destOffset++] = colorMap[key + 2];
        }
        return dest;
      }
      this.getRgbBuffer(src, srcOffset, count, dest, 0, bits);
      return dest;
    },
    /**
     * True if the colorspace has components in the default range of [0, 1].
     * This should be true for all colorspaces except for lab color spaces
     * which are [0,100], [-128, 127], [-128, 127].
     */
    usesZeroToOneRange: true
  };

  ColorSpace.parse = function ColorSpace_parse(cs, xref, res) {
    var IR = ColorSpace.parseToIR(cs, xref, res);
    if (IR instanceof AlternateCS)
      return IR;

    return ColorSpace.fromIR(IR);
  };

  ColorSpace.fromIR = function ColorSpace_fromIR(IR) {
    var name = isArray(IR) ? IR[0] : IR;

    switch (name) {
      case 'DeviceGrayCS':
        return new DeviceGrayCS();
      case 'DeviceRgbCS':
        return new DeviceRgbCS();
      case 'DeviceCmykCS':
        return new DeviceCmykCS();
      case 'PatternCS':
        var basePatternCS = IR[1];
        if (basePatternCS)
          basePatternCS = ColorSpace.fromIR(basePatternCS);
        return new PatternCS(basePatternCS);
      case 'IndexedCS':
        var baseIndexedCS = IR[1];
        var hiVal = IR[2];
        var lookup = IR[3];
        return new IndexedCS(ColorSpace.fromIR(baseIndexedCS), hiVal, lookup);
      case 'AlternateCS':
        var numComps = IR[1];
        var alt = IR[2];
        var tintFnIR = IR[3];

        return new AlternateCS(numComps, ColorSpace.fromIR(alt),
                                PDFFunction.fromIR(tintFnIR));
      case 'LabCS':
        var whitePoint = IR[1].WhitePoint;
        var blackPoint = IR[1].BlackPoint;
        var range = IR[1].Range;
        return new LabCS(whitePoint, blackPoint, range);
      default:
        error('Unkown name ' + name);
    }
    return null;
  };

  ColorSpace.parseToIR = function ColorSpace_parseToIR(cs, xref, res) {
    if (isName(cs)) {
      var colorSpaces = res.get('ColorSpace');
      if (isDict(colorSpaces)) {
        var refcs = colorSpaces.get(cs.name);
        if (refcs)
          cs = refcs;
      }
    }

    cs = xref.fetchIfRef(cs);
    var mode;

    if (isName(cs)) {
      mode = cs.name;
      this.mode = mode;

      switch (mode) {
        case 'DeviceGray':
        case 'G':
          return 'DeviceGrayCS';
        case 'DeviceRGB':
        case 'RGB':
          return 'DeviceRgbCS';
        case 'DeviceCMYK':
        case 'CMYK':
          return 'DeviceCmykCS';
        case 'Pattern':
          return ['PatternCS', null];
        default:
          error('unrecognized colorspace ' + mode);
      }
    } else if (isArray(cs)) {
      mode = cs[0].name;
      this.mode = mode;

      switch (mode) {
        case 'DeviceGray':
        case 'G':
          return 'DeviceGrayCS';
        case 'DeviceRGB':
        case 'RGB':
          return 'DeviceRgbCS';
        case 'DeviceCMYK':
        case 'CMYK':
          return 'DeviceCmykCS';
        case 'CalGray':
          return 'DeviceGrayCS';
        case 'CalRGB':
          return 'DeviceRgbCS';
        case 'ICCBased':
          var stream = xref.fetchIfRef(cs[1]);
          var dict = stream.dict;
          var numComps = dict.get('N');
          if (numComps == 1)
            return 'DeviceGrayCS';
          if (numComps == 3)
            return 'DeviceRgbCS';
          if (numComps == 4)
            return 'DeviceCmykCS';
          break;
        case 'Pattern':
          var basePatternCS = cs[1];
          if (basePatternCS)
            basePatternCS = ColorSpace.parseToIR(basePatternCS, xref, res);
          return ['PatternCS', basePatternCS];
        case 'Indexed':
        case 'I':
          var baseIndexedCS = ColorSpace.parseToIR(cs[1], xref, res);
          var hiVal = cs[2] + 1;
          var lookup = xref.fetchIfRef(cs[3]);
          if (isStream(lookup)) {
            lookup = lookup.getBytes();
          }
          return ['IndexedCS', baseIndexedCS, hiVal, lookup];
        case 'Separation':
        case 'DeviceN':
          var name = cs[1];
          var numComps = 1;
          if (isName(name))
            numComps = 1;
          else if (isArray(name))
            numComps = name.length;
          var alt = ColorSpace.parseToIR(cs[2], xref, res);
          var tintFnIR = PDFFunction.getIR(xref, xref.fetchIfRef(cs[3]));
          return ['AlternateCS', numComps, alt, tintFnIR];
        case 'Lab':
          var params = cs[1].getAll();
          return ['LabCS', params];
        default:
          error('unimplemented color space object "' + mode + '"');
      }
    } else {
      error('unrecognized color space object: "' + cs + '"');
    }
    return null;
  };
  /**
   * Checks if a decode map matches the default decode map for a color space.
   * This handles the general decode maps where there are two values per
   * component. e.g. [0, 1, 0, 1, 0, 1] for a RGB color.
   * This does not handle Lab, Indexed, or Pattern decode maps since they are
   * slightly different.
   * @param {Array} decode Decode map (usually from an image).
   * @param {Number} n Number of components the color space has.
   */
  ColorSpace.isDefaultDecode = function ColorSpace_isDefaultDecode(decode, n) {
    if (!decode)
      return true;

    if (n * 2 !== decode.length) {
      warn('The decode map is not the correct length');
      return true;
    }
    for (var i = 0, ii = decode.length; i < ii; i += 2) {
      if (decode[i] !== 0 || decode[i + 1] != 1)
        return false;
    }
    return true;
  };

  return ColorSpace;
})();

/**
 * Alternate color space handles both Separation and DeviceN color spaces.  A
 * Separation color space is actually just a DeviceN with one color component.
 * Both color spaces use a tinting function to convert colors to a base color
 * space.
 */
var AlternateCS = (function AlternateCSClosure() {
  function AlternateCS(numComps, base, tintFn) {
    this.name = 'Alternate';
    this.numComps = numComps;
    this.defaultColor = new Float32Array(numComps);
    for (var i = 0; i < numComps; ++i) {
      this.defaultColor[i] = 1;
    }
    this.base = base;
    this.tintFn = tintFn;
  }

  AlternateCS.prototype = {
    getRgb: function AlternateCS_getRgb(src, srcOffset) {
      var rgb = new Uint8Array(3);
      this.getRgbItem(src, srcOffset, rgb, 0);
      return rgb;
    },
    getRgbItem: function AlternateCS_getRgbItem(src, srcOffset,
                                                dest, destOffset) {
      var baseNumComps = this.base.numComps;
      var input = 'subarray' in src ?
        src.subarray(srcOffset, srcOffset + this.numComps) :
        Array.prototype.slice.call(src, srcOffset, srcOffset + this.numComps);
      var tinted = this.tintFn(input);
      this.base.getRgbItem(tinted, 0, dest, destOffset);
    },
    getRgbBuffer: function AlternateCS_getRgbBuffer(src, srcOffset, count,
                                                    dest, destOffset, bits) {
      var tintFn = this.tintFn;
      var base = this.base;
      var scale = 1 / ((1 << bits) - 1);
      var baseNumComps = base.numComps;
      var usesZeroToOneRange = base.usesZeroToOneRange;
      var isPassthrough = base.isPassthrough(8) || !usesZeroToOneRange;
      var pos = isPassthrough ? destOffset : 0;
      var baseBuf = isPassthrough ? dest : new Uint8Array(baseNumComps * count);
      var numComps = this.numComps;

      var scaled = new Float32Array(numComps);
      for (var i = 0; i < count; i++) {
        for (var j = 0; j < numComps; j++) {
          scaled[j] = src[srcOffset++] * scale;
        }
        var tinted = tintFn(scaled);
        if (usesZeroToOneRange) {
          for (var j = 0; j < baseNumComps; j++) {
            baseBuf[pos++] = tinted[j] * 255;
          }
        } else {
          base.getRgbItem(tinted, 0, baseBuf, pos);
          pos += baseNumComps;
        }
      }
      if (!isPassthrough) {
        base.getRgbBuffer(baseBuf, 0, count, dest, destOffset, 8);
      }
    },
    getOutputLength: function AlternateCS_getOutputLength(inputLength) {
      return this.base.getOutputLength(inputLength *
                                       this.base.numComps / this.numComps);
    },
    isPassthrough: ColorSpace.prototype.isPassthrough,
    createRgbBuffer: ColorSpace.prototype.createRgbBuffer,
    isDefaultDecode: function AlternateCS_isDefaultDecode(decodeMap) {
      return ColorSpace.isDefaultDecode(decodeMap, this.numComps);
    },
    usesZeroToOneRange: true
  };

  return AlternateCS;
})();

var PatternCS = (function PatternCSClosure() {
  function PatternCS(baseCS) {
    this.name = 'Pattern';
    this.base = baseCS;
  }
  PatternCS.prototype = {};

  return PatternCS;
})();

var IndexedCS = (function IndexedCSClosure() {
  function IndexedCS(base, highVal, lookup) {
    this.name = 'Indexed';
    this.numComps = 1;
    this.defaultColor = new Uint8Array([0]);
    this.base = base;
    this.highVal = highVal;

    var baseNumComps = base.numComps;
    var length = baseNumComps * highVal;
    var lookupArray;

    if (isStream(lookup)) {
      lookupArray = new Uint8Array(length);
      var bytes = lookup.getBytes(length);
      lookupArray.set(bytes);
    } else if (isString(lookup)) {
      lookupArray = new Uint8Array(length);
      for (var i = 0; i < length; ++i)
        lookupArray[i] = lookup.charCodeAt(i);
    } else if (lookup instanceof Uint8Array) {
      lookupArray = lookup;
    } else {
      error('Unrecognized lookup table: ' + lookup);
    }
    this.lookup = lookupArray;
  }

  IndexedCS.prototype = {
    getRgb: function IndexedCS_getRgb(src, srcOffset) {
      var numComps = this.base.numComps;
      var start = src[srcOffset] * numComps;
      return this.base.getRgb(this.lookup, start);
    },
    getRgbItem: function IndexedCS_getRgbItem(src, srcOffset,
                                              dest, destOffset) {
      var numComps = this.base.numComps;
      var start = src[srcOffset] * numComps;
      this.base.getRgbItem(this.lookup, start, dest, destOffset);
    },
    getRgbBuffer: function IndexedCS_getRgbBuffer(src, srcOffset, count,
                                                  dest, destOffset) {
      var base = this.base;
      var numComps = base.numComps;
      var outputDelta = base.getOutputLength(numComps);
      var lookup = this.lookup;

      for (var i = 0; i < count; ++i) {
        var lookupPos = src[srcOffset++] * numComps;
        base.getRgbBuffer(lookup, lookupPos, 1, dest, destOffset, 8);
        destOffset += outputDelta;
      }
    },
    getOutputLength: function IndexedCS_getOutputLength(inputLength) {
      return this.base.getOutputLength(inputLength * this.base.numComps);
    },
    isPassthrough: ColorSpace.prototype.isPassthrough,
    createRgbBuffer: ColorSpace.prototype.createRgbBuffer,
    isDefaultDecode: function IndexedCS_isDefaultDecode(decodeMap) {
      // indexed color maps shouldn't be changed
      return true;
    },
    usesZeroToOneRange: true
  };
  return IndexedCS;
})();

var DeviceGrayCS = (function DeviceGrayCSClosure() {
  function DeviceGrayCS() {
    this.name = 'DeviceGray';
    this.numComps = 1;
    this.defaultColor = new Float32Array([0]);
  }

  DeviceGrayCS.prototype = {
    getRgb: function DeviceGrayCS_getRgb(src, srcOffset) {
      var rgb = new Uint8Array(3);
      this.getRgbItem(src, srcOffset, rgb, 0);
      return rgb;
    },
    getRgbItem: function DeviceGrayCS_getRgbItem(src, srcOffset,
                                                 dest, destOffset) {
      var c = (src[srcOffset] * 255) | 0;
      c = c < 0 ? 0 : c > 255 ? 255 : c;
      dest[destOffset] = dest[destOffset + 1] = dest[destOffset + 2] = c;
    },
    getRgbBuffer: function DeviceGrayCS_getRgbBuffer(src, srcOffset, count,
                                                     dest, destOffset, bits) {
      var scale = 255 / ((1 << bits) - 1);
      var j = srcOffset, q = destOffset;
      for (var i = 0; i < count; ++i) {
        var c = (scale * src[j++]) | 0;
        dest[q++] = c;
        dest[q++] = c;
        dest[q++] = c;
      }
    },
    getOutputLength: function DeviceGrayCS_getOutputLength(inputLength) {
      return inputLength * 3;
    },
    isPassthrough: ColorSpace.prototype.isPassthrough,
    createRgbBuffer: ColorSpace.prototype.createRgbBuffer,
    isDefaultDecode: function DeviceGrayCS_isDefaultDecode(decodeMap) {
      return ColorSpace.isDefaultDecode(decodeMap, this.numComps);
    },
    usesZeroToOneRange: true
  };
  return DeviceGrayCS;
})();

var DeviceRgbCS = (function DeviceRgbCSClosure() {
  function DeviceRgbCS() {
    this.name = 'DeviceRGB';
    this.numComps = 3;
    this.defaultColor = new Float32Array([0, 0, 0]);
  }
  DeviceRgbCS.prototype = {
    getRgb: function DeviceRgbCS_getRgb(src, srcOffset) {
      var rgb = new Uint8Array(3);
      this.getRgbItem(src, srcOffset, rgb, 0);
      return rgb;
    },
    getRgbItem: function DeviceRgbCS_getRgbItem(src, srcOffset,
                                                dest, destOffset) {
      var r = (src[srcOffset] * 255) | 0;
      var g = (src[srcOffset + 1] * 255) | 0;
      var b = (src[srcOffset + 2] * 255) | 0;
      dest[destOffset] = r < 0 ? 0 : r > 255 ? 255 : r;
      dest[destOffset + 1] = g < 0 ? 0 : g > 255 ? 255 : g;
      dest[destOffset + 2] = b < 0 ? 0 : b > 255 ? 255 : b;
    },
    getRgbBuffer: function DeviceRgbCS_getRgbBuffer(src, srcOffset, count,
                                                    dest, destOffset, bits) {
      var length = count * 3;
      if (bits == 8) {
        dest.set(src.subarray(srcOffset, srcOffset + length), destOffset);
        return;
      }
      var scale = 255 / ((1 << bits) - 1);
      var j = srcOffset, q = destOffset;
      for (var i = 0; i < length; ++i) {
        dest[q++] = (scale * src[j++]) | 0;
      }
    },
    getOutputLength: function DeviceRgbCS_getOutputLength(inputLength) {
      return inputLength;
    },
    isPassthrough: function DeviceRgbCS_isPassthrough(bits) {
      return bits == 8;
    },
    createRgbBuffer: ColorSpace.prototype.createRgbBuffer,
    isDefaultDecode: function DeviceRgbCS_isDefaultDecode(decodeMap) {
      return ColorSpace.isDefaultDecode(decodeMap, this.numComps);
    },
    usesZeroToOneRange: true
  };
  return DeviceRgbCS;
})();

var DeviceCmykCS = (function DeviceCmykCSClosure() {
  // The coefficients below was found using numerical analysis: the method of
  // steepest descent for the sum((f_i - color_value_i)^2) for r/g/b colors,
  // where color_value is the tabular value from the table of sampled RGB colors
  // from CMYK US Web Coated (SWOP) colorspace, and f_i is the corresponding
  // CMYK color conversion using the estimation below:
  //   f(A, B,.. N) = Acc+Bcm+Ccy+Dck+c+Fmm+Gmy+Hmk+Im+Jyy+Kyk+Ly+Mkk+Nk+255
  function convertToRgb(src, srcOffset, srcScale, dest, destOffset) {
    var c = src[srcOffset + 0] * srcScale;
    var m = src[srcOffset + 1] * srcScale;
    var y = src[srcOffset + 2] * srcScale;
    var k = src[srcOffset + 3] * srcScale;

    var r =
      c * (-4.387332384609988 * c + 54.48615194189176 * m +
           18.82290502165302 * y + 212.25662451639585 * k +
           -285.2331026137004) +
      m * (1.7149763477362134 * m - 5.6096736904047315 * y +
           -17.873870861415444 * k - 5.497006427196366) +
      y * (-2.5217340131683033 * y - 21.248923337353073 * k +
           17.5119270841813) +
      k * (-21.86122147463605 * k - 189.48180835922747) + 255;
    var g =
      c * (8.841041422036149 * c + 60.118027045597366 * m +
           6.871425592049007 * y + 31.159100130055922 * k +
           -79.2970844816548) +
      m * (-15.310361306967817 * m + 17.575251261109482 * y +
           131.35250912493976 * k - 190.9453302588951) +
      y * (4.444339102852739 * y + 9.8632861493405 * k - 24.86741582555878) +
      k * (-20.737325471181034 * k - 187.80453709719578) + 255;
    var b = 
      c * (0.8842522430003296 * c + 8.078677503112928 * m +
           30.89978309703729 * y - 0.23883238689178934 * k +
           -14.183576799673286) +
      m * (10.49593273432072 * m + 63.02378494754052 * y +
           50.606957656360734 * k - 112.23884253719248) +
      y * (0.03296041114873217 * y + 115.60384449646641 * k +
           -193.58209356861505) +
      k * (-22.33816807309886 * k - 180.12613974708367) + 255;

    dest[destOffset] = r > 255 ? 255 : r < 0 ? 0 : r;
    dest[destOffset + 1] = g > 255 ? 255 : g < 0 ? 0 : g;
    dest[destOffset + 2] = b > 255 ? 255 : b < 0 ? 0 : b;
  }

  function DeviceCmykCS() {
    this.name = 'DeviceCMYK';
    this.numComps = 4;
    this.defaultColor = new Float32Array([0, 0, 0, 1]);
  }
  DeviceCmykCS.prototype = {
    getRgb: function DeviceCmykCS_getRgb(src, srcOffset) {
      var rgb = new Uint8Array(3);
      convertToRgb(src, srcOffset, 1, rgb, 0);
      return rgb;
    },
    getRgbItem: function DeviceCmykCS_getRgbItem(src, srcOffset,
                                                 dest, destOffset) {
      convertToRgb(src, srcOffset, 1, dest, destOffset);
    },
    getRgbBuffer: function DeviceCmykCS_getRgbBuffer(src, srcOffset, count,
                                                     dest, destOffset, bits) {
      var scale = 1 / ((1 << bits) - 1);
      for (var i = 0; i < count; i++) {
        convertToRgb(src, srcOffset, scale, dest, destOffset);
        srcOffset += 4;
        destOffset += 3;
      }
    },
    getOutputLength: function DeviceCmykCS_getOutputLength(inputLength) {
      return (inputLength >> 2) * 3;
    },
    isPassthrough: ColorSpace.prototype.isPassthrough,
    createRgbBuffer: ColorSpace.prototype.createRgbBuffer,
    isDefaultDecode: function DeviceCmykCS_isDefaultDecode(decodeMap) {
      return ColorSpace.isDefaultDecode(decodeMap, this.numComps);
    },
    usesZeroToOneRange: true
  };

  return DeviceCmykCS;
})();

//
// LabCS: Based on "PDF Reference, Sixth Ed", p.250
//
var LabCS = (function LabCSClosure() {
  function LabCS(whitePoint, blackPoint, range) {
    this.name = 'Lab';
    this.numComps = 3;
    this.defaultColor = new Float32Array([0, 0, 0]);

    if (!whitePoint)
      error('WhitePoint missing - required for color space Lab');
    blackPoint = blackPoint || [0, 0, 0];
    range = range || [-100, 100, -100, 100];

    // Translate args to spec variables
    this.XW = whitePoint[0];
    this.YW = whitePoint[1];
    this.ZW = whitePoint[2];
    this.amin = range[0];
    this.amax = range[1];
    this.bmin = range[2];
    this.bmax = range[3];

    // These are here just for completeness - the spec doesn't offer any
    // formulas that use BlackPoint in Lab
    this.XB = blackPoint[0];
    this.YB = blackPoint[1];
    this.ZB = blackPoint[2];

    // Validate vars as per spec
    if (this.XW < 0 || this.ZW < 0 || this.YW !== 1)
      error('Invalid WhitePoint components, no fallback available');

    if (this.XB < 0 || this.YB < 0 || this.ZB < 0) {
      info('Invalid BlackPoint, falling back to default');
      this.XB = this.YB = this.ZB = 0;
    }

    if (this.amin > this.amax || this.bmin > this.bmax) {
      info('Invalid Range, falling back to defaults');
      this.amin = -100;
      this.amax = 100;
      this.bmin = -100;
      this.bmax = 100;
    }
  }

  // Function g(x) from spec
  function fn_g(x) {
    if (x >= 6 / 29)
      return x * x * x;
    else
      return (108 / 841) * (x - 4 / 29);
  }

  function decode(value, high1, low2, high2) {
    return low2 + (value) * (high2 - low2) / (high1);
  }

  // If decoding is needed maxVal should be 2^bits per component - 1.
  function convertToRgb(cs, src, srcOffset, maxVal, dest, destOffset) {
    // XXX: Lab input is in the range of [0, 100], [amin, amax], [bmin, bmax]
    // not the usual [0, 1]. If a command like setFillColor is used the src
    // values will already be within the correct range. However, if we are
    // converting an image we have to map the values to the correct range given
    // above.
    // Ls,as,bs <---> L*,a*,b* in the spec
    var Ls = src[srcOffset];
    var as = src[srcOffset + 1];
    var bs = src[srcOffset + 2];
    if (maxVal !== false) {
      Ls = decode(Ls, maxVal, 0, 100);
      as = decode(as, maxVal, cs.amin, cs.amax);
      bs = decode(bs, maxVal, cs.bmin, cs.bmax);
    }

    // Adjust limits of 'as' and 'bs'
    as = as > cs.amax ? cs.amax : as < cs.amin ? cs.amin : as;
    bs = bs > cs.bmax ? cs.bmax : bs < cs.bmin ? cs.bmin : bs;

    // Computes intermediate variables X,Y,Z as per spec
    var M = (Ls + 16) / 116;
    var L = M + (as / 500);
    var N = M - (bs / 200);

    var X = cs.XW * fn_g(L);
    var Y = cs.YW * fn_g(M);
    var Z = cs.ZW * fn_g(N);

    var r, g, b;
    // Using different conversions for D50 and D65 white points,
    // per http://www.color.org/srgb.pdf
    if (cs.ZW < 1) {
      // Assuming D50 (X=0.9642, Y=1.00, Z=0.8249)
      r = X * 3.1339 + Y * -1.6170 + Z * -0.4906;
      g = X * -0.9785 + Y * 1.9160 + Z * 0.0333;
      b = X * 0.0720 + Y * -0.2290 + Z * 1.4057;
    } else {
      // Assuming D65 (X=0.9505, Y=1.00, Z=1.0888)
      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;
    }
    // clamp color values to [0,1] range then convert to [0,255] range.
    dest[destOffset] = Math.sqrt(r < 0 ? 0 : r > 1 ? 1 : r) * 255;
    dest[destOffset + 1] = Math.sqrt(g < 0 ? 0 : g > 1 ? 1 : g) * 255;
    dest[destOffset + 2] = Math.sqrt(b < 0 ? 0 : b > 1 ? 1 : b) * 255;
  }

  LabCS.prototype = {
    getRgb: function LabCS_getRgb(src, srcOffset) {
      var rgb = new Uint8Array(3);
      convertToRgb(this, src, srcOffset, false, rgb, 0);
      return rgb;
    },
    getRgbItem: function LabCS_getRgbItem(src, srcOffset, dest, destOffset) {
      convertToRgb(this, src, srcOffset, false, dest, destOffset);
    },
    getRgbBuffer: function LabCS_getRgbBuffer(src, srcOffset, count,
                                              dest, destOffset, bits) {
      var maxVal = (1 << bits) - 1;
      for (var i = 0; i < count; i++) {
        convertToRgb(this, src, srcOffset, maxVal, dest, destOffset);
        srcOffset += 3;
        destOffset += 3;
      }
    },
    getOutputLength: function LabCS_getOutputLength(inputLength) {
      return inputLength;
    },
    isPassthrough: ColorSpace.prototype.isPassthrough,
    isDefaultDecode: function LabCS_isDefaultDecode(decodeMap) {
      // XXX: Decoding is handled with the lab conversion because of the strange
      // ranges that are used.
      return true;
    },
    usesZeroToOneRange: false
  };
  return LabCS;
})();
