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65 lines
1.9 KiB
JavaScript
65 lines
1.9 KiB
JavaScript
/* This Source Code Form is subject to the terms of the Mozilla Public
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* License, v. 2.0. If a copy of the MPL was not distributed with this
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* file, You can obtain one at http://mozilla.org/MPL/2.0/. */
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/**
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* Given a color in the Lab space, return its chroma (colorfulness,
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* saturation).
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*
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* @param lab
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* The lab color to get the chroma from
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*
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* @return A number greater than zero that measures chroma in the image
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*/
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function labChroma(lab) {
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return Math.sqrt(Math.pow(lab.a, 2) + Math.pow(lab.b, 2));
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}
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/**
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* Given the RGB components of a color as integers from 0-255, return the
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* color in the XYZ color space.
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*
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* @return An object with x, y, z properties holding those components of the
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* color in the XYZ color space.
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*/
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function rgb2xyz(r, g, b) {
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r /= 255;
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g /= 255;
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b /= 255;
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// assume sRGB
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r = r > 0.04045 ? Math.pow(((r + 0.055) / 1.055), 2.4) : (r / 12.92);
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g = g > 0.04045 ? Math.pow(((g + 0.055) / 1.055), 2.4) : (g / 12.92);
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b = b > 0.04045 ? Math.pow(((b + 0.055) / 1.055), 2.4) : (b / 12.92);
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return {
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x: ((r * 0.4124) + (g * 0.3576) + (b * 0.1805)) * 100,
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y: ((r * 0.2126) + (g * 0.7152) + (b * 0.0722)) * 100,
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z: ((r * 0.0193) + (g * 0.1192) + (b * 0.9505)) * 100
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};
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}
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/**
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* Given the RGB components of a color as integers from 0-255, return the
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* color in the Lab color space.
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*
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* @return An object with lightness, a, b properties holding those components
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* of the color in the Lab color space.
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*/
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function rgb2lab(r, g, b) {
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let xyz = rgb2xyz(r, g, b),
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x = xyz.x / 95.047,
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y = xyz.y / 100,
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z = xyz.z / 108.883;
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x = x > 0.008856 ? Math.pow(x, 1/3) : (7.787 * x) + (16 / 116);
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y = y > 0.008856 ? Math.pow(y, 1/3) : (7.787 * y) + (16 / 116);
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z = z > 0.008856 ? Math.pow(z, 1/3) : (7.787 * z) + (16 / 116);
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return {
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lightness: (116 * y) - 16,
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a: 500 * (x - y),
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b: 200 * (y - z)
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};
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}
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