69 lines
1.4 KiB
JavaScript
69 lines
1.4 KiB
JavaScript
/**
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* https://en.wikipedia.org/?title=YPbPr
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*
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* YPbPr is analog form of YCbCr
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* hence limits are [0..1]
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*
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* Default conversion is ITU-R BT.709
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*
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* @module color-space/ypbpr
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*/
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import rgb from './rgb.js';
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var ypbpr = ({
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name: 'ypbpr',
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min: [0, -0.5, -0.5],
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max: [1, 0.5, 0.5],
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channel: ['Y', 'Pb', 'Pr'],
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alias: ['YPbPr', 'Y/PB/PR', 'YPRPB', 'PRPBY', 'PBPRY', 'Y/Pb/Pr', 'YPrPb', 'PrPbY', 'PbPrY', 'Y/R-Y/B-Y', 'Y(R-Y)(B-Y)', 'R-Y', 'B-Y']
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});
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/**
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* YPbPr to RGB
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*
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* @param {Array<number>} ypbpr RGB values
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* @param {number} kb
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* @param {number} kr
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* @return {Array<number>} YPbPr values
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*/
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ypbpr.rgb = function (ypbpr, kb, kr) {
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var y = ypbpr[0], pb = ypbpr[1], pr = ypbpr[2];
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//default conversion is ITU-R BT.709
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kb = kb || 0.0722;
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kr = kr || 0.2126;
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var r = y + 2 * pr * (1 - kr);
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var b = y + 2 * pb * (1 - kb);
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var g = (y - kr * r - kb * b) / (1 - kr - kb);
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return [r * 255, g * 255, b * 255];
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};
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/**
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* RGB to YPbPr
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*
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* @param {Array<number>} rgb YPbPr values
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* @param {number} kb
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* @param {number} kr
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* @return {Array<number>} RGB values
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*/
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rgb.ypbpr = function (rgb, kb, kr) {
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var r = rgb[0] / 255, g = rgb[1] / 255, b = rgb[2] / 255;
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//ITU-R BT.709
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kb = kb || 0.0722;
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kr = kr || 0.2126;
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var y = kr * r + (1 - kr - kb) * g + kb * b;
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var pb = 0.5 * (b - y) / (1 - kb);
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var pr = 0.5 * (r - y) / (1 - kr);
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return [y, pb, pr];
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};
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export default ypbpr;
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