Server/frontend/src/lib/utils/color.ts

import type { ColorHS, ColorRGB, ColorXY } from "$lib/models/color";

import XY_MAP from "./color-xy.json";
import K_MAP from "./color-k.json";

export function rgbToHex(rgb: ColorRGB): string {
  const r = Math.min(Math.round(rgb.red * 255), 255).toString(16).padStart(2, "0");
  const g = Math.min(Math.round(rgb.green * 255), 255).toString(16).padStart(2, "0");
  const b = Math.min(Math.round(rgb.blue * 255), 255).toString(16).padStart(2, "0");
  return ["#", r, g, b].join("");
}

export function kToRgb(k: number) {
  if (k < 1000) {
    k = 1000;
  }
  if (k > 12000) {
    k = 12000;
  }

  const key = (Math.round(k / 50) * 50).toFixed(0);

  return (K_MAP as Record<string, ColorRGB>)[key];
}

export function xyToRgb(xy: ColorXY) {
  const x = (Math.round((xy.x||0) * 100) / 100);
  const y = (Math.round((xy.y||0) * 100) / 100);

  return (XY_MAP as Record<string, ColorRGB>)[`${x.toFixed(2)},${y.toFixed(2)}`];
}

export function hsToHsl(hs: ColorHS): string {
  const l=1-(hs.sat/2);
  const m=Math.min(l,1-l);

  return `hsl(${hs.hue}, ${(m?(1-l)/m:0)*100}%, ${l*100}%)`;
}

export function rgb2hsv (rgb: ColorRGB): ColorHS {
  const r = rgb.red;
  const g = rgb.green;
  const b = rgb.blue;

  let rabs: number, gabs: number, babs: number;
  let rr: number, gg: number, bb: number;
  let h: number = 0, s: number = 0, v: number;
  let diff: number;

  const diffc = (c: number) => (v - c) / 6 / diff + 1 / 2;
  const percentRoundFn = (num: number) => Math.round(num * 100) / 100;

  rabs = r / 255;
  gabs = g / 255;
  babs = b / 255;
  v = Math.max(rabs, gabs, babs),
  diff = v - Math.min(rabs, gabs, babs);
  if (diff == 0) {
      h = s = 0;
  } else {
      s = diff / v;
      rr = diffc(rabs);
      gg = diffc(gabs);
      bb = diffc(babs);

      if (rabs === v) {
          h = bb - gg;
      } else if (gabs === v) {
          h = (1 / 3) + rr - bb;
      } else if (babs === v) {
          h = (2 / 3) + gg - rr;
      }
      if (h < 0) {
          h += 1;
      } else if (h > 1) {
          h -= 1;
      }
  }

  return {
      hue: Math.round(h * 360),
      sat: s,
  };
}