04Brightness-Band Posterize

<main class="stage">
<div class="vd is-demo" id="vdRoot">
  <canvas class="vd__canvas" id="vdCanvas" width="480" height="300"></canvas>
  <input class="vd__range" id="vdRange" type="range" min="2" max="8" value="4" step="1" aria-label="posterize band count">
  <p class="vd__caption">A Posterize That Splits Brightness Into Bands</p>
</div>
</main>

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

.vd {
  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;
}

.vd__canvas {
  display: block;
  width: 100%;
  height: 100%;
}

.vd__caption {
  position: absolute;
  left: $sp-3;
  bottom: $sp-3;
  max-width: 72%;
  margin: 0;
  padding: $sp-1 $sp-3;
  border-radius: $r-pill;
  background: rgba(23, 20, 26, .78);
  color: $subject-cream;
  font-weight: 500;
  font-size: 12px;
  line-height: 1.4;
  pointer-events: none;
}

.vd__range {
  position: absolute;
  left: $sp-3;
  right: $sp-3;
  top: $sp-3;
  margin: 0;
  accent-color: $subject-blue-deep;
  cursor: pointer;
}

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

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

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

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

.vd {
  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);
}

.vd__canvas {
  display: block;
  width: 100%;
  height: 100%;
}

.vd__caption {
  position: absolute;
  left: 12px;
  bottom: 12px;
  max-width: 72%;
  margin: 0;
  padding: 4px 12px;
  border-radius: 999px;
  background: rgba(23, 20, 26, 0.78);
  color: #fff7e6;
  font-weight: 500;
  font-size: 12px;
  line-height: 1.4;
  pointer-events: none;
}

.vd__range {
  position: absolute;
  left: 12px;
  right: 12px;
  top: 12px;
  margin: 0;
  accent-color: #0a4fe8;
  cursor: pointer;
}

@media (max-width: 340px) {
  .vd__caption {
    font-size: 10px;
    padding: 4px 8px;
  }
}
@media (prefers-reduced-motion: reduce) {
  .vd {
    cursor: default;
  }
}

(function () {
  var root = document.getElementById('vdRoot');
  var canvas = document.getElementById('vdCanvas');
  var ctx = canvas.getContext('2d');
  var wrap = canvas.parentElement;

  function seedRand(seed) {
    var s = seed >>> 0;
    return function () { s = (s * 1664525 + 1013904223) >>> 0; return s / 4294967296; };
  }

  function drawScene(pctx, w, h, seed) {
    var rand = seedRand(seed);
    var sky = pctx.createLinearGradient(0, 0, 0, h);
    sky.addColorStop(0, '#8fc7ff');
    sky.addColorStop(1, '#fff2d6');
    pctx.fillStyle = sky;
    pctx.fillRect(0, 0, w, h);
    var sunX = w * 0.72, sunY = h * 0.28, sunR = h * 0.2;
    var glow = pctx.createRadialGradient(sunX, sunY, 0, sunX, sunY, sunR * 2.4);
    glow.addColorStop(0, 'rgba(255,247,230,.9)');
    glow.addColorStop(1, 'rgba(255,247,230,0)');
    pctx.fillStyle = glow;
    pctx.fillRect(0, 0, w, h);
    pctx.beginPath();
    pctx.arc(sunX, sunY, sunR, 0, Math.PI * 2);
    pctx.fillStyle = '#ffe27a';
    pctx.fill();
    var hillColors = ['#6ec8ff', '#2b9d74', '#17141a'];
    for (var i = 0; i < 3; i += 1) {
      var baseY = h * (0.48 + i * 0.16);
      pctx.beginPath();
      pctx.moveTo(0, h);
      var step = Math.max(2, w / 24);
      for (var x = 0; x <= w; x += step) {
        var n = Math.sin(x * 0.06 + i * 2.4 + seed * 0.0003) * h * 0.05 + Math.sin(x * 0.17 + i) * h * 0.02;
        pctx.lineTo(x, baseY + n);
      }
      pctx.lineTo(w, h);
      pctx.closePath();
      pctx.fillStyle = hillColors[i];
      pctx.fill();
    }
    var accent = ['#ff5c8a', '#2fe6c6', '#ffb703', '#8a5cd6', '#3ddc97', '#ff7a5e'];
    for (var m = 0; m < 8; m += 1) {
      var ax = rand() * w, ay = h * (0.56 + rand() * 0.38), ar = h * (0.025 + rand() * 0.05);
      pctx.beginPath();
      pctx.arc(ax, ay, ar, 0, Math.PI * 2);
      pctx.fillStyle = accent[m % accent.length];
      pctx.fill();
    }
    for (var k = 0; k < 60; k += 1) {
      var px = rand() * w, py = rand() * h * 0.5, r = rand() * 1.3 + 0.3;
      pctx.beginPath();
      pctx.arc(px, py, r, 0, Math.PI * 2);
      pctx.fillStyle = 'rgba(255,255,255,' + (0.12 + rand() * 0.22) + ')';
      pctx.fill();
    }
  }

  function quantizeBand(buf, w, h, bands, outBuf) {
    var step = 255 / (bands - 1);
    for (var i = 0; i < w * h; i += 1) {
      var idx = i * 4;
      for (var c = 0; c < 3; c += 1) {
        var v = buf[idx + c];
        outBuf[idx + c] = Math.max(0, Math.min(255, Math.round(Math.round(v / step) * step)));
      }
      outBuf[idx + 3] = 255;
    }
  }

  var range = document.getElementById('vdRange');
  var CALC_W = 160, CALC_H = 100;
  var LOOP_MS = 2000;
  var POSTERIZE_BAND_COUNT = 4;

  var off = document.createElement('canvas');
  off.width = CALC_W; off.height = CALC_H;
  var octx = off.getContext('2d');
  drawScene(octx, CALC_W, CALC_H, 415041);
  var baseImg = octx.getImageData(0, 0, CALC_W, CALC_H);
  var baseBuf = baseImg.data;

  var out = document.createElement('canvas');
  out.width = CALC_W; out.height = CALC_H;
  var outCtx = out.getContext('2d');
  var outImg = outCtx.createImageData(CALC_W, CALC_H);
  var outBuf = outImg.data;

  var userBands = POSTERIZE_BAND_COUNT;
  if (range) {
    range.value = String(userBands);
    range.addEventListener('input', function () {
      userBands = Number(range.value);
      if (reduce) draw(lastElapsed);
    });
  }

  function renderFrame(t) {
    var wave = Math.sin(t * Math.PI * 4 / LOOP_MS) * 2;
    var bands = Math.max(2, Math.min(8, Math.round(userBands + wave)));
    quantizeBand(baseBuf, CALC_W, CALC_H, bands, outBuf);
  }

  var cw = 480, ch = 300;
  function fit() {
    var r = wrap.getBoundingClientRect();
    cw = Math.max(1, Math.round(r.width));
    ch = Math.max(1, Math.round(r.height));
    canvas.width = cw; canvas.height = ch;
    draw(lastElapsed);
  }

  var lastElapsed = 0;

  function draw(elapsed) {
    lastElapsed = elapsed;
    renderFrame(elapsed);
    outCtx.putImageData(outImg, 0, 0);
    ctx.imageSmoothingEnabled = false;
    ctx.clearRect(0, 0, cw, ch);
    ctx.drawImage(out, 0, 0, CALC_W, CALC_H, 0, 0, cw, ch);
  }

  var reduce = window.matchMedia('(prefers-reduced-motion: reduce)').matches;
  var playing = !reduce;
  var elapsed = reduce ? LOOP_MS * 0.5 : 0;
  if (reduce) { root.classList.remove('is-demo'); }

  var lastTs = null;
  function tick(ts) {
    if (lastTs === null) lastTs = ts;
    var dt = ts - lastTs;
    lastTs = ts;
    if (playing) {
      elapsed += dt;
      if (elapsed >= LOOP_MS) elapsed -= LOOP_MS;
    }
    draw(elapsed);
    requestAnimationFrame(tick);
  }
  fit();
  window.addEventListener('resize', fit);
  draw(elapsed);
  requestAnimationFrame(tick);

})();

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

export default function PixelPosterizeBand() {
  const rootRef = useRef<HTMLDivElement>(null);
  const canvasRef = useRef<HTMLCanvasElement>(null);
  const rangeRef = useRef<HTMLInputElement>(null);

  useEffect(() => {
    const root = rootRef.current;
    const canvas = canvasRef.current;
    if (!root || !canvas) return;
    const ctx = canvas.getContext("2d");
    if (!ctx) return;
    const wrap = canvas.parentElement as HTMLElement;
    const range = rangeRef.current;

    function seedRand(seed: number) {
      let s = seed >>> 0;
      return function () { s = (s * 1664525 + 1013904223) >>> 0; return s / 4294967296; };
    }

    function drawScene(pctx: CanvasRenderingContext2D, w: number, h: number, seed: number) {
      const rand = seedRand(seed);
      const sky = pctx.createLinearGradient(0, 0, 0, h);
      sky.addColorStop(0, "#8fc7ff");
      sky.addColorStop(1, "#fff2d6");
      pctx.fillStyle = sky;
      pctx.fillRect(0, 0, w, h);
      const sunX = w * 0.72, sunY = h * 0.28, sunR = h * 0.2;
      const glow = pctx.createRadialGradient(sunX, sunY, 0, sunX, sunY, sunR * 2.4);
      glow.addColorStop(0, "rgba(255,247,230,.9)");
      glow.addColorStop(1, "rgba(255,247,230,0)");
      pctx.fillStyle = glow;
      pctx.fillRect(0, 0, w, h);
      pctx.beginPath();
      pctx.arc(sunX, sunY, sunR, 0, Math.PI * 2);
      pctx.fillStyle = "#ffe27a";
      pctx.fill();
      const hillColors = ["#6ec8ff", "#2b9d74", "#17141a"];
      for (let i = 0; i < 3; i += 1) {
        const baseY = h * (0.48 + i * 0.16);
        pctx.beginPath();
        pctx.moveTo(0, h);
        const step = Math.max(2, w / 24);
        for (let x = 0; x <= w; x += step) {
          const n = Math.sin(x * 0.06 + i * 2.4 + seed * 0.0003) * h * 0.05 + Math.sin(x * 0.17 + i) * h * 0.02;
          pctx.lineTo(x, baseY + n);
        }
        pctx.lineTo(w, h);
        pctx.closePath();
        pctx.fillStyle = hillColors[i];
        pctx.fill();
      }
      const accent = ["#ff5c8a", "#2fe6c6", "#ffb703", "#8a5cd6", "#3ddc97", "#ff7a5e"];
      for (let m = 0; m < 8; m += 1) {
        const ax = rand() * w, ay = h * (0.56 + rand() * 0.38), ar = h * (0.025 + rand() * 0.05);
        pctx.beginPath();
        pctx.arc(ax, ay, ar, 0, Math.PI * 2);
        pctx.fillStyle = accent[m % accent.length];
        pctx.fill();
      }
      for (let k = 0; k < 60; k += 1) {
        const px = rand() * w, py = rand() * h * 0.5, r = rand() * 1.3 + 0.3;
        pctx.beginPath();
        pctx.arc(px, py, r, 0, Math.PI * 2);
        pctx.fillStyle = "rgba(255,255,255," + (0.12 + rand() * 0.22) + ")";
        pctx.fill();
      }
    }

    function quantizeBand(buf: Uint8ClampedArray, w: number, h: number, bands: number, outBuf: Uint8ClampedArray) {
      const step = 255 / (bands - 1);
      for (let i = 0; i < w * h; i += 1) {
        const idx = i * 4;
        for (let c = 0; c < 3; c += 1) {
          const v = buf[idx + c];
          outBuf[idx + c] = Math.max(0, Math.min(255, Math.round(Math.round(v / step) * step)));
        }
        outBuf[idx + 3] = 255;
      }
    }

    const CALC_W = 160, CALC_H = 100;
    const LOOP_MS = 2000;
    const POSTERIZE_BAND_COUNT = 4;

    const off = document.createElement("canvas");
    off.width = CALC_W; off.height = CALC_H;
    const octx = off.getContext("2d") as CanvasRenderingContext2D;
    drawScene(octx, CALC_W, CALC_H, 415041);
    const baseImg = octx.getImageData(0, 0, CALC_W, CALC_H);
    const baseBuf = baseImg.data;

    const out = document.createElement("canvas");
    out.width = CALC_W; out.height = CALC_H;
    const outCtx = out.getContext("2d") as CanvasRenderingContext2D;
    const outImg = outCtx.createImageData(CALC_W, CALC_H);
    const outBuf = outImg.data;

    let userBands = POSTERIZE_BAND_COUNT;
    if (range) {
      range.value = String(userBands);
      range.addEventListener("input", function () {
        userBands = Number(range.value);
        if (reduce) draw(lastElapsed);
      });
    }

    function renderFrame(t: number) {
      const wave = Math.sin(t * Math.PI * 4 / LOOP_MS) * 2;
      const bands = Math.max(2, Math.min(8, Math.round(userBands + wave)));
      quantizeBand(baseBuf, CALC_W, CALC_H, bands, outBuf);
    }

    let cw = 480, ch = 300;
    function fit() {
      const r = wrap.getBoundingClientRect();
      cw = Math.max(1, Math.round(r.width));
      ch = Math.max(1, Math.round(r.height));
      canvas!.width = cw; canvas!.height = ch;
      draw(lastElapsed);
    }

    let lastElapsed = 0;
    function draw(elapsed: number) {
      lastElapsed = elapsed;
      renderFrame(elapsed);
      outCtx.putImageData(outImg, 0, 0);
      ctx!.imageSmoothingEnabled = false;
      ctx!.clearRect(0, 0, cw, ch);
      ctx!.drawImage(out, 0, 0, CALC_W, CALC_H, 0, 0, cw, ch);
    }

    const reduce = window.matchMedia("(prefers-reduced-motion: reduce)").matches;
    let playing = !reduce;
    let elapsed = reduce ? LOOP_MS * 0.5 : 0;
    if (reduce) { root.classList.remove("is-demo"); }

    let lastTs: number | null = null;
    let raf = 0;
    function tick(ts: number) {
      if (lastTs === null) lastTs = ts;
      const dt = ts - lastTs;
      lastTs = ts;
      if (playing) {
        elapsed += dt;
        if (elapsed >= LOOP_MS) elapsed -= LOOP_MS;
      }
      draw(elapsed);
      raf = requestAnimationFrame(tick);
    }
    fit();
    window.addEventListener("resize", fit);
    draw(elapsed);
    raf = requestAnimationFrame(tick);

    return () => {
      cancelAnimationFrame(raf);
      window.removeEventListener("resize", fit);
    };
  }, []);

  return (
    <main className={styles.stage}>
      <div className={`${styles.vd} is-demo`} ref={rootRef}>
        <canvas className={styles.vd__canvas} ref={canvasRef} width={480} height={300} />
        <input className={styles.vd__range} ref={rangeRef} type="range" min={2} max={8} defaultValue={4} step={1} aria-label="posterize band count" />
        <p className={styles.vd__caption}>명도 구간을 나누는 포스터라이즈</p>
      </div>
    </main>
  );
}