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uvw.js
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uvw.js
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/**
* https://en.wikipedia.org/wiki/CIE_1964_color_space
*
* Very similar to LUV, but w and v are calculated a bit differently.
*
* @module color-space/uvw
*/
import ucs from './ucs.js';
import xyz from './xyz.js';
var uvw = {
name: 'uvw',
min: [-134, -140, 0],
max: [224, 122, 100],
channel: ['U','V','W'],
alias: ['UVW', 'cieuvw', 'cie1964']
};
export default uvw;
/**
* UVW to XYZ
*/
uvw.xyz = function (arg, i, o) {
var _u, _v, w, u, v, x, y, z, xn, yn, zn, un, vn;
u = arg[0], v = arg[1], w = arg[2];
if (w === 0) return [0,0,0];
//get illuminant/observer
i = i || 'D65';
o = o || 2;
xn = xyz.whitepoint[o][i][0];
yn = xyz.whitepoint[o][i][1];
zn = xyz.whitepoint[o][i][2];
un = (4 * xn) / (xn + (15 * yn) + (3 * zn));
vn = (6 * yn) / (xn + (15 * yn) + (3 * zn));
y = Math.pow((w + 17) / 25, 3);
_u = u / (13 * w) + un || 0;
_v = v / (13 * w) + vn || 0;
x = (6 / 4) * y * _u / _v;
z = y * (2 / _v - 0.5 * _u / _v - 5);
return [x, y, z];
};
/**
* XYZ to UVW
*
* @return {Array} An UVW array
*/
xyz.uvw = function (arr, i, o) {
var x = arr[0], y = arr[1], z = arr[2], xn, yn, zn, un, vn;
//find out normal source u v
i = i || 'D65';
o = o || 2;
xn = xyz.whitepoint[o][i][0];
yn = xyz.whitepoint[o][i][1];
zn = xyz.whitepoint[o][i][2];
un = (4 * xn) / (xn + (15 * yn) + (3 * zn));
vn = (6 * yn) / (xn + (15 * yn) + (3 * zn));
var _u = 4 * x / (x + 15 * y + 3 * z) || 0;
var _v = 6 * y / (x + 15 * y + 3 * z) || 0;
//calc values
var w = 25 * Math.pow(y, 1/3) - 17;
var u = 13 * w * (_u - un);
var v = 13 * w * (_v - vn);
return [u, v, w];
};
/**
* UVW to UCS
*
* @param {Array} uvw UCS values
*
* @return {Array} UVW values
*/
uvw.ucs = function(uvw) {
//find chromacity variables
};
/**
* UCS to UVW
*
* @param {Array} uvw UVW values
*
* @return {Array} UCS values
*/
ucs.uvw = function(ucs) {
// //find chromacity variables
// var u = U / (U + V + W);
// var v = V / (U + V + W);
// //find 1964 UVW
// w = 25 * Math.pow(y, 1/3) - 17;
// u = 13 * w * (u - un);
// v = 13 * w * (v - vn);
};