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

React rendering primitives for stratigraphic columns

import Color from "../Color.js";
import "../io/lab/index.js";
import scale from "./scale.js";
const binom_row = function(n) {
  let row = [1, 1];
  for (let i = 1; i < n; i++) {
    let newrow = [1];
    for (let j = 1; j <= row.length; j++) {
      newrow[j] = (row[j] || 0) + row[j - 1];
    }
    row = newrow;
  }
  return row;
};
const bezier = function(colors) {
  let I, lab0, lab1, lab2;
  colors = colors.map((c) => new Color(c));
  if (colors.length === 2) {
    [lab0, lab1] = colors.map((c) => c.lab());
    I = function(t) {
      const lab = [0, 1, 2].map((i) => lab0[i] + t * (lab1[i] - lab0[i]));
      return new Color(lab, "lab");
    };
  } else if (colors.length === 3) {
    [lab0, lab1, lab2] = colors.map((c) => c.lab());
    I = function(t) {
      const lab = [0, 1, 2].map(
        (i) => (1 - t) * (1 - t) * lab0[i] + 2 * (1 - t) * t * lab1[i] + t * t * lab2[i]
      );
      return new Color(lab, "lab");
    };
  } else if (colors.length === 4) {
    let lab3;
    [lab0, lab1, lab2, lab3] = colors.map((c) => c.lab());
    I = function(t) {
      const lab = [0, 1, 2].map(
        (i) => (1 - t) * (1 - t) * (1 - t) * lab0[i] + 3 * (1 - t) * (1 - t) * t * lab1[i] + 3 * (1 - t) * t * t * lab2[i] + t * t * t * lab3[i]
      );
      return new Color(lab, "lab");
    };
  } else if (colors.length >= 5) {
    let labs, row, n;
    labs = colors.map((c) => c.lab());
    n = colors.length - 1;
    row = binom_row(n);
    I = function(t) {
      const u = 1 - t;
      const lab = [0, 1, 2].map(
        (i) => labs.reduce(
          (sum, el, j) => sum + row[j] * u ** (n - j) * t ** j * el[i],
          0
        )
      );
      return new Color(lab, "lab");
    };
  } else {
    throw new RangeError("No point in running bezier with only one color.");
  }
  return I;
};
const bezier$1 = (colors) => {
  const f = bezier(colors);
  f.scale = () => scale(f);
  return f;
};
export {
  bezier$1 as default
};
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