ndvi.js

// Comment test
var ndviFunc = function({ h, s, v }, [_r, _g, _b, _a]) {

  if (_r === 0 && _g === 0 && _b === 0) {
    _a = 0;
  }

  let r, g, b, i, f, p, q, t;

  i = Math.floor(h * 6);
  f = h * 6 - i;
  p = v * (1 - s);
  q = v * (1 - f * s);
  t = v * (1 - (1 - f) * s);
  switch (i % 6) {
    case 0: r = v; g = t; b = p; break;
    case 1: r = q; g = v; b = p; break;
    case 2: r = p; g = v; b = t; break;
    case 3: r = p; g = q; b = v; break;
    case 4: r = t; g = p; b = v; break;
    case 5: r = v; g = p; b = q; break;
  }

  return {
    r: Math.round(r * 255),
    g: Math.round(g * 255),
    b: Math.round(b * 255),
    a: _a
  };
};

self.addEventListener('message', function(e) {
  var data = e.data;

  for (let i = 0; i < data.data.length; i += 4) {
    let NDVI = data.data[i] / 255;
    let hsv_in = { h: NDVI * 0.33333, s: 1, v: 1 };

    let {r, g, b, a} = ndviFunc(hsv_in, [data.data[i], data.data[i + 1], data.data[i + 2], data.data[i + 3]]);

    data.data[i] = r;
    data.data[i + 1] = g;
    data.data[i + 2] = b;
    data.data[i + 3] = a;
  }

  self.postMessage({ message: data });
});