06Grain Dither That Erases Banding

<main class="stage">
<div class="mg is-demo" id="mgRoot">
  <canvas class="mg__canvas" id="mgCanvas" width="160" height="100" tabindex="0" aria-label="A low-contrast mesh shows its steps as bands, so a seeded noise smaller than one step is added per pixel to scatter the rounding edges and erase them."></canvas>
  <p class="mg__status" id="mgStatus" aria-live="polite">Demo running</p>
  <button class="mg__btn" id="mgBtn" type="button">Pause</button>
  <p class="mg__caption">A low-contrast mesh shows its steps as bands, so a seeded noise smaller than one step is added per pixel to scatter the rounding edges and erase them.</p>
</div>
</main>

@use "../../../../site/static/demo-tokens" as *;
@include stage($stage-ink);

.mg {
  position: relative;
  width: min(92vw, calc(160vh - 12.8vw));
  aspect-ratio: 480 / 300;
  margin: 0 auto;
  border-radius: $r-card;
  overflow: hidden;
  box-shadow: $shadow-raised;
  background: $subject-cream;
}

.mg__canvas {
  display: block;
  width: 100%;
  height: 100%;
  touch-action: none;
}

.mg__canvas:focus-visible {
  outline: 2px solid rgba(23, 20, 26, .85);
  outline-offset: -6px;
}

.mg__status {
  position: absolute;
  left: $sp-3;
  top: $sp-3;
  max-width: 70%;
  margin: 0;
  padding: $sp-1 $sp-3;
  border-radius: $r-pill;
  background: rgba(255, 255, 255, .85);
  color: $subject-ink;
  font-weight: 500;
  font-size: 11px;
  line-height: 1.4;
  pointer-events: none;
}

.mg__btn {
  position: absolute;
  right: $sp-3;
  bottom: $sp-3;
  margin: 0;
  padding: $sp-1 $sp-3;
  border: 0;
  border-radius: $r-pill;
  background: rgba(255, 255, 255, .85);
  color: $subject-ink;
  font: inherit;
  font-weight: 500;
  font-size: 12px;
  line-height: 1.4;
  cursor: pointer;
}

.mg__btn:focus-visible {
  outline: 2px solid $subject-ink;
  outline-offset: 2px;
}

.mg__caption {
  position: absolute;
  left: $sp-3;
  bottom: $sp-3;
  max-width: 68%;
  margin: 0;
  padding: $sp-1 $sp-3;
  border-radius: $r-pill;
  background: rgba(255, 255, 255, .85);
  color: $subject-ink;
  font-weight: 500;
  font-size: 12px;
  line-height: 1.4;
  pointer-events: none;
}

@media (max-width: 340px) {
  .mg__caption, .mg__btn { font-size: 10px; padding: $sp-1 $sp-2; }
  .mg__status { font-size: 10px; }
}

@media (prefers-reduced-motion: reduce) {
  .mg { cursor: default; }
}

html, body {
  margin: 0;
  overflow: hidden;
}

.stage {
  box-sizing: border-box;
  min-height: 100vh;
  display: grid;
  place-items: center;
  margin: 0;
  background: #17141a;
  font-family: -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
  padding: clamp(8px, 4vw, 24px);
}

.mg {
  position: relative;
  width: min(92vw, 160vh - 12.8vw);
  aspect-ratio: 480/300;
  margin: 0 auto;
  border-radius: 16px;
  overflow: hidden;
  box-shadow: 0 14px 24px rgba(23, 20, 26, 0.32);
  background: #fff7e6;
}

.mg__canvas {
  display: block;
  width: 100%;
  height: 100%;
  touch-action: none;
}

.mg__canvas:focus-visible {
  outline: 2px solid rgba(23, 20, 26, 0.85);
  outline-offset: -6px;
}

.mg__status {
  position: absolute;
  left: 12px;
  top: 12px;
  max-width: 70%;
  margin: 0;
  padding: 4px 12px;
  border-radius: 999px;
  background: rgba(255, 255, 255, 0.85);
  color: #17141a;
  font-weight: 500;
  font-size: 11px;
  line-height: 1.4;
  pointer-events: none;
}

.mg__btn {
  position: absolute;
  right: 12px;
  bottom: 12px;
  margin: 0;
  padding: 4px 12px;
  border: 0;
  border-radius: 999px;
  background: rgba(255, 255, 255, 0.85);
  color: #17141a;
  font: inherit;
  font-weight: 500;
  font-size: 12px;
  line-height: 1.4;
  cursor: pointer;
}

.mg__btn:focus-visible {
  outline: 2px solid #17141a;
  outline-offset: 2px;
}

.mg__caption {
  position: absolute;
  left: 12px;
  bottom: 12px;
  max-width: 68%;
  margin: 0;
  padding: 4px 12px;
  border-radius: 999px;
  background: rgba(255, 255, 255, 0.85);
  color: #17141a;
  font-weight: 500;
  font-size: 12px;
  line-height: 1.4;
  pointer-events: none;
}

@media (max-width: 340px) {
  .mg__caption, .mg__btn {
    font-size: 10px;
    padding: 4px 8px;
  }
  .mg__status {
    font-size: 10px;
  }
}
@media (prefers-reduced-motion: reduce) {
  .mg {
    cursor: default;
  }
}

(function () {
  var root = document.getElementById('mgRoot');
  var canvas = document.getElementById('mgCanvas');
  var statusEl = document.getElementById('mgStatus');
  var btnEl = document.getElementById('mgBtn');
  function main(root, canvas, statusEl, btnEl) {
      var ctx0 = canvas.getContext('2d');
      if (!ctx0) {
          return function () { return; };
      }
      var ctx = ctx0;
      var CALC_W = 160, CALC_H = 100;
      var FIXED_DT = 16;
      var REDUCE_STEP_MS = 900;
      var reduce = window.matchMedia('(prefers-reduced-motion: reduce)').matches;
      if (reduce)
          root.classList.remove('is-demo');
      var paused = false;
      var elapsed = 0, rafId = 0;
      var cleaners = [];
      function listen(target, type, fn) {
          target.addEventListener(type, fn);
          cleaners.push(function () { target.removeEventListener(type, fn); });
      }
      function clamp(v, lo, hi) { return v < lo ? lo : (v > hi ? hi : v); }
      function lerp(a, b, k) { return a + (b - a) * k; }
      function smooth(x) { var c = clamp(x, 0, 1); return c * c * (3 - 2 * c); }
      function setStatus(msg) { statusEl.textContent = msg; }
      // 시드 고정 난수 (mulberry32) — 같은 시드는 언제나 같은 수열이다
      function seedRand(seed) {
          var s = seed >>> 0;
          return function () {
              s = (s + 0x6D2B79F5) >>> 0;
              var z = s;
              z = Math.imul(z ^ (z >>> 15), z | 1);
              z ^= z + Math.imul(z ^ (z >>> 7), z | 61);
              return ((z ^ (z >>> 14)) >>> 0) / 4294967296;
          };
      }
      // 파스텔 여섯 색 — 분홍·라일락·하늘·민트·살구·버터
      var PAL = [[255, 152, 178], [182, 152, 255], [122, 200, 255], [122, 222, 186], [255, 196, 140], [255, 228, 130]];
      // 색 목록을 원형으로 읽는다. pos 의 정수부는 몇 번째 색, 소수부는 다음 색으로 넘어가는 정도
      function pick(pal, pos, out) {
          var n = pal.length;
          var i0 = Math.floor(pos);
          var f = pos - i0;
          var a = pal[((i0 % n) + n) % n];
          var b = pal[(((i0 + 1) % n) + n) % n];
          out[0] = lerp(a[0], b[0], f);
          out[1] = lerp(a[1], b[1], f);
          out[2] = lerp(a[2], b[2], f);
      }
      function put(d, x, y, r, g, b) {
          var o = (y * CALC_W + x) * 4;
          d[o] = r;
          d[o + 1] = g;
          d[o + 2] = b;
          d[o + 3] = 255;
      }
      canvas.width = CALC_W;
      canvas.height = CALC_H;
      var img = ctx.createImageData(CALC_W, CALC_H);
      var px = img.data;
      // 06 알갱이 디더 — 같은 어두운 그라데이션을 8비트보다 거친 STEP 단계로 반올림해, 왼쪽은 그대로 오른쪽은 알갱이를 더한다
      var REDUCE_MS = 900;
      var STEP = 10;
      var GRAIN = 1;
      var DARK = [30, 34, 66];
      var LIGHT = [112, 100, 170];
      var NOISE_N = CALC_W * CALC_H;
      var noiseTab = [];
      var rnd = seedRand(2026);
      for (var ni = 0; ni < NOISE_N; ni += 1) {
          noiseTab.push(rnd());
      }
      function paint(t, d) {
          var cx = 0.5 + 0.28 * Math.sin(6.2832 * t * 0.4);
          var cy = 0.5 + 0.2 * Math.cos(6.2832 * t * 0.31);
          var frame = Math.floor(t * 30);
          for (var y = 0; y < CALC_H; y += 1) {
              var v = y / (CALC_H - 1);
              for (var x = 0; x < CALC_W; x += 1) {
                  var u = x / (CALC_W - 1);
                  var dx = (u - cx) * 1.6, dy = v - cy;
                  var k = 1 - clamp(Math.sqrt(dx * dx + dy * dy) * 1.05, 0, 1);
                  var right = x >= CALC_W / 2;
                  var n = noiseTab[(y * CALC_W + x + frame * 997) % NOISE_N];
                  // 반올림 문턱을 픽셀마다 0.5 ± GRAIN/2 단계 안에서 흔든다 (왼쪽은 문턱 0.5 고정)
                  var th = right ? 0.5 + (n - 0.5) * GRAIN : 0.5;
                  var ch = [0, 0, 0];
                  for (var c = 0; c < 3; c += 1) {
                      var val = lerp(DARK[c], LIGHT[c], k);
                      ch[c] = Math.floor(val / STEP + th) * STEP;
                  }
                  if (x === Math.floor(CALC_W / 2) || x === Math.floor(CALC_W / 2) - 1) {
                      ch = [236, 232, 255];
                  }
                  put(d, x, y, ch[0], ch[1], ch[2]);
              }
          }
      }
      function draw() {
          paint(elapsed / 1000, px);
          ctx.putImageData(img, 0, 0);
      }
      var lastTs = null;
      var accMs = 0;
      function tick(ts) {
          if (lastTs === null) {
              lastTs = ts;
          }
          var frameDt = Math.min(ts - lastTs, 48);
          lastTs = ts;
          if (!paused) {
              accMs += frameDt;
              while (accMs >= FIXED_DT) {
                  elapsed += FIXED_DT;
                  accMs -= FIXED_DT;
              }
              draw();
          }
          rafId = requestAnimationFrame(tick);
      }
      function onButton() {
          root.classList.remove('is-demo');
          if (reduce) {
              elapsed += REDUCE_STEP_MS;
              draw();
              setStatus('Stepping one scene at a time');
              return;
          }
          paused = !paused;
          btnEl.textContent = paused ? 'Play' : 'Pause';
          setStatus(paused ? 'Paused' : 'Demo running');
      }
      draw();
      listen(btnEl, 'click', function () { onButton(); });
      listen(canvas, 'pointerdown', function () { onButton(); });
      listen(canvas, 'keydown', function (e) {
          var k = e.key;
          if (k === 'Enter' || k === ' ') {
              e.preventDefault();
              onButton();
          }
      });
      if (reduce) {
          elapsed = REDUCE_MS;
          draw();
          btnEl.textContent = 'Next scene';
          setStatus('Stepping one scene at a time');
      }
      else {
          rafId = requestAnimationFrame(tick);
      }
      function destroy() {
          cancelAnimationFrame(rafId);
          for (var i = 0; i < cleaners.length; i += 1) {
              cleaners[i]();
          }
      }
      return destroy;
  }
  main(root, canvas, statusEl, btnEl);
})();

import { useEffect, useRef } from "react";
import styles from "./MgGrainDitherBandingRemoval.module.scss";

function main(root: HTMLDivElement, canvas: HTMLCanvasElement, statusEl: HTMLElement, btnEl: HTMLButtonElement): () => void {
  var ctx0 = canvas.getContext('2d');
  if (!ctx0) { return function (): void { return; }; }
  var ctx: CanvasRenderingContext2D = ctx0;
  var CALC_W = 160, CALC_H = 100;
  var FIXED_DT = 16;
  var REDUCE_STEP_MS = 900;
  var reduce = window.matchMedia('(prefers-reduced-motion: reduce)').matches;
  if (reduce) root.classList.remove('is-demo');
  var paused = false;
  var elapsed = 0, rafId = 0;
  var cleaners: Array<() => void> = [];

  function listen(target: EventTarget, type: string, fn: (e: Event) => void): void {
    target.addEventListener(type, fn);
    cleaners.push(function (): void { target.removeEventListener(type, fn); });
  }
  function clamp(v: number, lo: number, hi: number): number { return v < lo ? lo : (v > hi ? hi : v); }
  function lerp(a: number, b: number, k: number): number { return a + (b - a) * k; }
  function smooth(x: number): number { var c = clamp(x, 0, 1); return c * c * (3 - 2 * c); }
  function setStatus(msg: string): void { statusEl.textContent = msg; }
  // 시드 고정 난수 (mulberry32) — 같은 시드는 언제나 같은 수열이다
  function seedRand(seed: number): () => number {
    var s = seed >>> 0;
    return function (): number {
      s = (s + 0x6D2B79F5) >>> 0;
      var z = s;
      z = Math.imul(z ^ (z >>> 15), z | 1);
      z ^= z + Math.imul(z ^ (z >>> 7), z | 61);
      return ((z ^ (z >>> 14)) >>> 0) / 4294967296;
    };
  }
  // 파스텔 여섯 색 — 분홍·라일락·하늘·민트·살구·버터
  var PAL: number[][] = [[255, 152, 178], [182, 152, 255], [122, 200, 255], [122, 222, 186], [255, 196, 140], [255, 228, 130]];
  // 색 목록을 원형으로 읽는다. pos 의 정수부는 몇 번째 색, 소수부는 다음 색으로 넘어가는 정도
  function pick(pal: number[][], pos: number, out: number[]): void {
    var n = pal.length;
    var i0 = Math.floor(pos);
    var f = pos - i0;
    var a = pal[((i0 % n) + n) % n];
    var b = pal[(((i0 + 1) % n) + n) % n];
    out[0] = lerp(a[0], b[0], f);
    out[1] = lerp(a[1], b[1], f);
    out[2] = lerp(a[2], b[2], f);
  }
  function put(d: Uint8ClampedArray, x: number, y: number, r: number, g: number, b: number): void {
    var o = (y * CALC_W + x) * 4;
    d[o] = r;
    d[o + 1] = g;
    d[o + 2] = b;
    d[o + 3] = 255;
  }

  canvas.width = CALC_W;
  canvas.height = CALC_H;
  var img = ctx.createImageData(CALC_W, CALC_H);
  var px = img.data;

  // 06 알갱이 디더 — 같은 어두운 그라데이션을 8비트보다 거친 STEP 단계로 반올림해, 왼쪽은 그대로 오른쪽은 알갱이를 더한다
  var REDUCE_MS = 900;
  var STEP = 10;
  var GRAIN = 1;
  var DARK: number[] = [30, 34, 66];
  var LIGHT: number[] = [112, 100, 170];
  var NOISE_N = CALC_W * CALC_H;
  var noiseTab: number[] = [];
  var rnd = seedRand(2026);
  for (var ni = 0; ni < NOISE_N; ni += 1) { noiseTab.push(rnd()); }
  function paint(t: number, d: Uint8ClampedArray): void {
    var cx = 0.5 + 0.28 * Math.sin(6.2832 * t * 0.4);
    var cy = 0.5 + 0.2 * Math.cos(6.2832 * t * 0.31);
    var frame = Math.floor(t * 30);
    for (var y = 0; y < CALC_H; y += 1) {
      var v = y / (CALC_H - 1);
      for (var x = 0; x < CALC_W; x += 1) {
        var u = x / (CALC_W - 1);
        var dx = (u - cx) * 1.6, dy = v - cy;
        var k = 1 - clamp(Math.sqrt(dx * dx + dy * dy) * 1.05, 0, 1);
        var right = x >= CALC_W / 2;
        var n = noiseTab[(y * CALC_W + x + frame * 997) % NOISE_N];
        // 반올림 문턱을 픽셀마다 0.5 ± GRAIN/2 단계 안에서 흔든다 (왼쪽은 문턱 0.5 고정)
        var th = right ? 0.5 + (n - 0.5) * GRAIN : 0.5;
        var ch: number[] = [0, 0, 0];
        for (var c = 0; c < 3; c += 1) {
          var val = lerp(DARK[c], LIGHT[c], k);
          ch[c] = Math.floor(val / STEP + th) * STEP;
        }
        if (x === Math.floor(CALC_W / 2) || x === Math.floor(CALC_W / 2) - 1) { ch = [236, 232, 255]; }
        put(d, x, y, ch[0], ch[1], ch[2]);
      }
    }
  }

  function draw(): void {
    paint(elapsed / 1000, px);
    ctx.putImageData(img, 0, 0);
  }
  var lastTs: number | null = null;
  var accMs = 0;
  function tick(ts: number): void {
    if (lastTs === null) { lastTs = ts; }
    var frameDt = Math.min(ts - lastTs, 48);
    lastTs = ts;
    if (!paused) {
      accMs += frameDt;
      while (accMs >= FIXED_DT) {
        elapsed += FIXED_DT;
        accMs -= FIXED_DT;
      }
      draw();
    }
    rafId = requestAnimationFrame(tick);
  }
  function onButton(): void {
    root.classList.remove('is-demo');
    if (reduce) {
      elapsed += REDUCE_STEP_MS;
      draw();
      setStatus('한 장면씩 넘기는 중');
      return;
    }
    paused = !paused;
    btnEl.textContent = paused ? '재생' : '멈춤';
    setStatus(paused ? '일시정지됨' : '시연 중');
  }
  draw();
  listen(btnEl, 'click', function (): void { onButton(); });
  listen(canvas, 'pointerdown', function (): void { onButton(); });
  listen(canvas, 'keydown', function (e: Event): void {
    var k = (e as KeyboardEvent).key;
    if (k === 'Enter' || k === ' ') { e.preventDefault(); onButton(); }
  });
  if (reduce) {
    elapsed = REDUCE_MS;
    draw();
    btnEl.textContent = '다음 장면';
    setStatus('한 장면씩 넘기는 중');
  } else {
    rafId = requestAnimationFrame(tick);
  }

  function destroy(): void {
    cancelAnimationFrame(rafId);
    for (var i = 0; i < cleaners.length; i += 1) { cleaners[i](); }
  }
  return destroy;
}

export default function MgGrainDitherBandingRemoval() {
  const rootRef = useRef<HTMLDivElement | null>(null);
  const canvasRef = useRef<HTMLCanvasElement | null>(null);
  const statusRef = useRef<HTMLParagraphElement | null>(null);
  const btnRef = useRef<HTMLButtonElement | null>(null);

  useEffect(() => {
    const root = rootRef.current;
    const canvas = canvasRef.current;
    const statusEl = statusRef.current;
    const btnEl = btnRef.current;
    if (!root || !canvas || !statusEl || !btnEl) return;
    return main(root, canvas, statusEl, btnEl);
  }, []);

  return (
    <main className={styles.stage}>
      <div className={`${styles.mg} is-demo`} ref={rootRef}>
        <canvas className={styles.mg__canvas} ref={canvasRef} width={160} height={100} tabIndex={0} aria-label="명암 차가 작은 메쉬는 단계가 띠로 보이는데, 픽셀마다 시드 고정 노이즈를 한 단계 안에서 더해 반올림 경계를 흩어 띠를 지운다." />
        <p className={styles.mg__status} ref={statusRef} aria-live="polite">시연 중</p>
        <button className={styles.mg__btn} ref={btnRef} type="button">멈춤</button>
        <p className={styles.mg__caption}>명암 차가 작은 메쉬는 단계가 띠로 보이는데, 픽셀마다 시드 고정 노이즈를 한 단계 안에서 더해 반올림 경계를 흩어 띠를 지운다.</p>
      </div>
    </main>
  );
}