mysticsymbolic.github.io/lib/random-colors.ts

import { Random } from "./random";
import { range } from "./util";
import * as colorspaces from "colorspaces";

/**
 * Clamp the given number to be between 0 and 255, then
 * convert it to hexadecimal.
 */
export function clampedByteToHex(value: number): string {
  if (value < 0) {
    value = 0;
  } else if (value > 255) {
    value = 255;
  }
  let hex = value.toString(16);
  if (hex.length === 1) {
    hex = "0" + hex;
  }
  return hex;
}

function createRandomColor(rng: Random): string {
  const max_luv_samples = 100;
  let luv_sample_failed = true;
  let rand_color_hex: string = "#000000";

  //See if we can pull out a sample inside the LUV solid
  for (let i = 0; i < max_luv_samples; i++) {
    let L = rng.inRange({ min: 0, max: 100, step: 1 });
    let u = rng.inRange({ min: -128, max: 128, step: 1 });
    let v = rng.inRange({ min: -128, max: 128, step: 1 });
    let rand_color = colorspaces.make_color("CIELUV", [L, u, v]);

    if (rand_color.is_displayable()) {
      rand_color_hex = rand_color.as("hex");
      luv_sample_failed = false;
      break;
    }
  }

  //just sample sRGB if I couldn't sample a random LUV color
  if (luv_sample_failed) {
    console.log("Sampling sRGB");
    let rgb = new Array<number>(3).map(() =>
      rng.inRange({ min: 0, max: 255, step: 1 })
    );
    console.log(rgb);
    for (let i = 0; i < rgb.length; i++) {
      rgb[i] = rgb[i] / 255.0;
    }
    console.log(rgb);
    let rand_color = colorspaces.make_color("sRGB", rgb);
    rand_color_hex = rand_color.as("hex");
  }

  return rand_color_hex;
}

/**
 * Create a random color palette with the given number of
 * entries, optionally using the given random number generator.
 *
 * The return value is an Array of strings, where each string is
 * a color hex hash (e.g. `#ff0000`).
 */
export function createRandomColorPalette(
  numEntries: number,
  rng: Random = new Random()
): string[] {
  return range(numEntries).map(() => createRandomColor(rng));
}