mirror of https://github.com/thangisme/notes.git
114 lines
3.6 KiB
JavaScript
114 lines
3.6 KiB
JavaScript
/**
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* @author Markus Ekholm
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* @copyright 2012-2015 (c) Markus Ekholm <markus at botten dot org >
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* @license Copyright (c) 2012-2015, Markus Ekholm
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* All rights reserved.
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions are met:
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* * Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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* * Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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* * Neither the name of the <organization> nor the
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* names of its contributors may be used to endorse or promote products
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* derived from this software without specific prior written permission.
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*
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* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
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* ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
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* WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
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* DISCLAIMED. IN NO EVENT SHALL MARKUS EKHOLM BE LIABLE FOR ANY
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* DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
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* (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
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* LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
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* ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
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* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*/
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/**
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* EXPORTS
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*/
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exports.rgb_to_lab = rgb_to_lab;
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/**
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* IMPORTS
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*/
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var pow = Math.pow;
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var sqrt = Math.sqrt;
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/**
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* API FUNCTIONS
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*/
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/**
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* Returns c converted to labcolor.
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* @param {rgbcolor} c should have fields R,G,B
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* @return {labcolor} c converted to labcolor
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*/
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function rgb_to_lab(c)
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{
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return xyz_to_lab(rgb_to_xyz(c))
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}
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/**
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* Returns c converted to xyzcolor.
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* @param {rgbcolor} c should have fields R,G,B
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* @return {xyzcolor} c converted to xyzcolor
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*/
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function rgb_to_xyz(c)
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{
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// Based on http://www.easyrgb.com/index.php?X=MATH&H=02
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var R = ( c.R / 255 );
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var G = ( c.G / 255 );
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var B = ( c.B / 255 );
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if ( R > 0.04045 ) R = pow(( ( R + 0.055 ) / 1.055 ),2.4);
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else R = R / 12.92;
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if ( G > 0.04045 ) G = pow(( ( G + 0.055 ) / 1.055 ),2.4);
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else G = G / 12.92;
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if ( B > 0.04045 ) B = pow(( ( B + 0.055 ) / 1.055 ), 2.4);
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else B = B / 12.92;
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R *= 100;
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G *= 100;
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B *= 100;
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// Observer. = 2°, Illuminant = D65
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var X = R * 0.4124 + G * 0.3576 + B * 0.1805;
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var Y = R * 0.2126 + G * 0.7152 + B * 0.0722;
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var Z = R * 0.0193 + G * 0.1192 + B * 0.9505;
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return {'X' : X, 'Y' : Y, 'Z' : Z};
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}
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/**
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* Returns c converted to labcolor.
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* @param {xyzcolor} c should have fields X,Y,Z
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* @return {labcolor} c converted to labcolor
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*/
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function xyz_to_lab(c)
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{
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// Based on http://www.easyrgb.com/index.php?X=MATH&H=07
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var ref_Y = 100.000;
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var ref_Z = 108.883;
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var ref_X = 95.047; // Observer= 2°, Illuminant= D65
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var Y = c.Y / ref_Y;
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var Z = c.Z / ref_Z;
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var X = c.X / ref_X;
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if ( X > 0.008856 ) X = pow(X, 1/3);
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else X = ( 7.787 * X ) + ( 16 / 116 );
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if ( Y > 0.008856 ) Y = pow(Y, 1/3);
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else Y = ( 7.787 * Y ) + ( 16 / 116 );
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if ( Z > 0.008856 ) Z = pow(Z, 1/3);
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else Z = ( 7.787 * Z ) + ( 16 / 116 );
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var L = ( 116 * Y ) - 16;
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var a = 500 * ( X - Y );
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var b = 200 * ( Y - Z );
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return {'L' : L , 'a' : a, 'b' : b};
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}
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// Local Variables:
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// allout-layout: t
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// js-indent-level: 2
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// End:
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