@macrostrat/column-components/dist/chroma-js/src/generator/average.js

React rendering primitives for stratigraphic columns

import Color from "../Color.js";
import clip_rgb from "../utils/clip_rgb.js";
import "../utils/type.js";
const { pow, sqrt, PI, cos, sin, atan2 } = Math;
const average = (colors, mode = "lrgb", weights = null) => {
  const l = colors.length;
  if (!weights) weights = Array.from(new Array(l)).map(() => 1);
  const k = l / weights.reduce(function(a, b) {
    return a + b;
  });
  weights.forEach((w, i) => {
    weights[i] *= k;
  });
  colors = colors.map((c) => new Color(c));
  if (mode === "lrgb") {
    return _average_lrgb(colors, weights);
  }
  const first = colors.shift();
  const xyz = first.get(mode);
  const cnt = [];
  let dx = 0;
  let dy = 0;
  for (let i = 0; i < xyz.length; i++) {
    xyz[i] = (xyz[i] || 0) * weights[0];
    cnt.push(isNaN(xyz[i]) ? 0 : weights[0]);
    if (mode.charAt(i) === "h" && !isNaN(xyz[i])) {
      const A = xyz[i] / 180 * PI;
      dx += cos(A) * weights[0];
      dy += sin(A) * weights[0];
    }
  }
  let alpha = first.alpha() * weights[0];
  colors.forEach((c, ci) => {
    const xyz2 = c.get(mode);
    alpha += c.alpha() * weights[ci + 1];
    for (let i = 0; i < xyz.length; i++) {
      if (!isNaN(xyz2[i])) {
        cnt[i] += weights[ci + 1];
        if (mode.charAt(i) === "h") {
          const A = xyz2[i] / 180 * PI;
          dx += cos(A) * weights[ci + 1];
          dy += sin(A) * weights[ci + 1];
        } else {
          xyz[i] += xyz2[i] * weights[ci + 1];
        }
      }
    }
  });
  for (let i = 0; i < xyz.length; i++) {
    if (mode.charAt(i) === "h") {
      let A = atan2(dy / cnt[i], dx / cnt[i]) / PI * 180;
      while (A < 0) A += 360;
      while (A >= 360) A -= 360;
      xyz[i] = A;
    } else {
      xyz[i] = xyz[i] / cnt[i];
    }
  }
  alpha /= l;
  return new Color(xyz, mode).alpha(alpha > 0.99999 ? 1 : alpha, true);
};
const _average_lrgb = (colors, weights) => {
  const l = colors.length;
  const xyz = [0, 0, 0, 0];
  for (let i = 0; i < colors.length; i++) {
    const col = colors[i];
    const f = weights[i] / l;
    const rgb = col._rgb;
    xyz[0] += pow(rgb[0], 2) * f;
    xyz[1] += pow(rgb[1], 2) * f;
    xyz[2] += pow(rgb[2], 2) * f;
    xyz[3] += rgb[3] * f;
  }
  xyz[0] = sqrt(xyz[0]);
  xyz[1] = sqrt(xyz[1]);
  xyz[2] = sqrt(xyz[2]);
  if (xyz[3] > 0.9999999) xyz[3] = 1;
  return new Color(clip_rgb(xyz));
};
export {
  average as default
};
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