01Card That Auto-Peels Once Pixel-Measured Area Passes a Threshold

<main class="stage">
<div class="scv is-demo" id="scv">
  <div class="scv__card">
    <p class="scv__label">Scratch card</p>
    <div class="scv__zone" id="zone">
      <div class="scv__prize">
        <p class="scv__prizeTitle">20% off coupon</p>
        <p class="scv__prizeSub">Scratch to see the result</p>
      </div>
      <canvas class="scv__foil" id="foil" width="280" height="150" aria-hidden="true"></canvas>
    </div>
    <div class="scv__meter" aria-hidden="true"><div class="scv__meterFill" id="meterFill"></div></div>
    <button type="button" class="scv__reveal" id="revealBtn">Reveal instantly</button>
    <p class="scv__live" id="live" aria-live="polite"></p>
  </div>
</div>
</main>

@use "../../../../site/static/demo-tokens" as *;

// 스크래치 카드 01 — 실제 긁기는 canvas destination-out. 긁힌 알파 픽셀 비율을
// clearedPixelRatio() 로 계산해 SCRATCH_REVEAL_THRESHOLD_PCT 를 넘으면 autoPeelRemaining() 이
// 나머지를 한 번에 지운다. 격자 미리보기(.is-demo)는 같은 함수를 스케줄로 호출한다.

@include stage($stage-ink);

.scv { display: flex; justify-content: center; width: 100%; }
.scv__card {
  width: min(100%, 300px); background: $subject-blue-deep; color: $subject-cream;
  border-radius: $r-card; box-shadow: $shadow-raised; padding: $sp-4;
}
.scv__label { margin: 0 0 $sp-1; font-weight: 800; font-size: 12px; letter-spacing: .04em; }
.scv__zone {
  position: relative; border-radius: $r-control; overflow: hidden;
  aspect-ratio: 280 / 150; background: $stage-paper;
}
.scv__prize {
  position: absolute; inset: 0; display: flex; flex-direction: column; align-items: center;
  justify-content: center; gap: $sp-1; text-align: center; padding: $sp-2;
}
.scv__prizeTitle { margin: 0; font-weight: 800; font-size: clamp(18px, 6vw, 22px); color: $subject-blue-deep; }
.scv__prizeSub { margin: 0; font-weight: 700; font-size: 11px; color: rgba(23, 20, 26, .68); }
.scv__foil { position: absolute; inset: 0; width: 100%; height: 100%; touch-action: none; }
.scv.is-open .scv__foil { visibility: hidden; }
.scv__meter { margin-top: $sp-1; height: $sp-1; border-radius: $r-pill; background: rgba(255, 255, 255, .28); overflow: hidden; }
.scv__meterFill { height: 100%; width: 0%; background: $subject-cream; border-radius: inherit; }
.scv__reveal {
  margin-top: $sp-1; border: 0; cursor: pointer; background: $subject-cream; color: $subject-blue-deep;
  border-radius: $r-pill; font-family: inherit; font-weight: 800; font-size: 11px; padding: $sp-1 $sp-3; line-height: 1.3;
}
.scv__reveal:focus-visible { outline: 3px solid $stage-paper; outline-offset: 2px; }
.scv__live { margin: $sp-1 0 0; min-height: 1em; font-weight: 700; font-size: 10px; color: $subject-cream; }

@media (max-width: 340px) {
  .scv__card { padding: $sp-3; }
  .scv__prizeTitle { font-size: 16px; }
}

@media (max-height: 220px) {
  .stage { padding: $sp-2; }
  .scv__card { padding: $sp-2 $sp-3; }
  .scv__label { margin: 0 0 $sp-1; }
  .scv__zone { aspect-ratio: 280 / 76; }
  .scv__meter { margin-top: $sp-1; }
  .scv__reveal { margin-top: $sp-1; }
  .scv__live { margin-top: $sp-1; min-height: .9em; }
}


@media (prefers-reduced-motion: reduce) {
  .scv { 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);
}

.scv {
  display: flex;
  justify-content: center;
  width: 100%;
}

.scv__card {
  width: min(100%, 300px);
  background: #0a4fe8;
  color: #fff7e6;
  border-radius: 16px;
  box-shadow: 0 14px 24px rgba(23, 20, 26, 0.32);
  padding: 16px;
}

.scv__label {
  margin: 0 0 4px;
  font-weight: 800;
  font-size: 12px;
  letter-spacing: 0.04em;
}

.scv__zone {
  position: relative;
  border-radius: 12px;
  overflow: hidden;
  aspect-ratio: 280/150;
  background: #ffffff;
}

.scv__prize {
  position: absolute;
  inset: 0;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  gap: 4px;
  text-align: center;
  padding: 8px;
}

.scv__prizeTitle {
  margin: 0;
  font-weight: 800;
  font-size: clamp(18px, 6vw, 22px);
  color: #0a4fe8;
}

.scv__prizeSub {
  margin: 0;
  font-weight: 700;
  font-size: 11px;
  color: rgba(23, 20, 26, 0.68);
}

.scv__foil {
  position: absolute;
  inset: 0;
  width: 100%;
  height: 100%;
  touch-action: none;
}

.scv.is-open .scv__foil {
  visibility: hidden;
}

.scv__meter {
  margin-top: 4px;
  height: 4px;
  border-radius: 999px;
  background: rgba(255, 255, 255, 0.28);
  overflow: hidden;
}

.scv__meterFill {
  height: 100%;
  width: 0%;
  background: #fff7e6;
  border-radius: inherit;
}

.scv__reveal {
  margin-top: 4px;
  border: 0;
  cursor: pointer;
  background: #fff7e6;
  color: #0a4fe8;
  border-radius: 999px;
  font-family: inherit;
  font-weight: 800;
  font-size: 11px;
  padding: 4px 12px;
  line-height: 1.3;
}

.scv__reveal:focus-visible {
  outline: 3px solid #ffffff;
  outline-offset: 2px;
}

.scv__live {
  margin: 4px 0 0;
  min-height: 1em;
  font-weight: 700;
  font-size: 10px;
  color: #fff7e6;
}

@media (max-width: 340px) {
  .scv__card {
    padding: 12px;
  }
  .scv__prizeTitle {
    font-size: 16px;
  }
}
@media (max-height: 220px) {
  .stage {
    padding: 8px;
  }
  .scv__card {
    padding: 8px 12px;
  }
  .scv__label {
    margin: 0 0 4px;
  }
  .scv__zone {
    aspect-ratio: 280/76;
  }
  .scv__meter {
    margin-top: 4px;
  }
  .scv__reveal {
    margin-top: 4px;
  }
  .scv__live {
    margin-top: 4px;
    min-height: 0.9em;
  }
}
@media (prefers-reduced-motion: reduce) {
  .scv {
    cursor: default;
  }
}

(function () {
  // 기법: 긁을 때마다 canvas getImageData 로 지워진 알파 픽셀 수를 세어 전체 대비 비율을
  // 계산한다. 그 비율이 SCRATCH_REVEAL_THRESHOLD_PCT 를 넘으면 나머지 은박을 한 번에
  // destination-out 으로 지워 자동으로 카드를 연다 — 픽셀 계산 하나가 판정을 만든다.
  var root = document.getElementById('scv');
  var zone = document.getElementById('zone');
  var foil = document.getElementById('foil');
  var ctx = foil.getContext('2d');
  var meterFill = document.getElementById('meterFill');
  var revealBtn = document.getElementById('revealBtn');
  var live = document.getElementById('live');

  var SCRATCH_REVEAL_THRESHOLD_PCT = 50;
  var SCRATCH_BRUSH_R = 15;
  var opened = false;

  function seedRand(seed) {
    var s = seed >>> 0;
    return function () { s = (s * 1664525 + 1013904223) >>> 0; return s / 4294967296; };
  }
  var foilRand = seedRand(424011);

  function paintFoil() {
    ctx.globalCompositeOperation = 'source-over';
    ctx.clearRect(0, 0, foil.width, foil.height);
    var grad = ctx.createLinearGradient(0, 0, foil.width, foil.height);
    grad.addColorStop(0, '#cfd3dd');
    grad.addColorStop(.5, '#eef0f5');
    grad.addColorStop(1, '#b9bdc9');
    ctx.fillStyle = grad;
    ctx.fillRect(0, 0, foil.width, foil.height);
    ctx.strokeStyle = 'rgba(23,20,26,.16)';
    ctx.lineWidth = 1;
    for (var i = 0; i < 22; i += 1) {
      var x = foilRand() * foil.width, y = foilRand() * foil.height;
      ctx.beginPath();
      ctx.moveTo(x, y);
      ctx.lineTo(x + (foilRand() * 22 - 11), y + (foilRand() * 8 - 4));
      ctx.stroke();
    }
  }

  function scratchAt(x, y) {
    ctx.globalCompositeOperation = 'destination-out';
    ctx.beginPath();
    ctx.arc(x, y, SCRATCH_BRUSH_R, 0, Math.PI * 2);
    ctx.fill();
  }

  function clearedPixelRatio() {
    var data = ctx.getImageData(0, 0, foil.width, foil.height).data;
    var clear = 0, total = data.length / 4;
    for (var i = 3; i < data.length; i += 4) { if (data[i] < 40) clear += 1; }
    return clear / total;
  }

  function updateMeter(ratio) {
    meterFill.style.width = Math.round(ratio * 100) + '%';
  }

  function openCard() {
    if (opened) return;
    opened = true;
    ctx.globalCompositeOperation = 'destination-out';
    ctx.fillRect(0, 0, foil.width, foil.height);
    updateMeter(1);
    root.classList.add('is-open');
    live.textContent = 'The 20% off coupon is revealed';
  }

  function autoPeelRemaining(ratio) {
    if (ratio * 100 >= SCRATCH_REVEAL_THRESHOLD_PCT) openCard();
  }

  function pos(e) {
    var r = foil.getBoundingClientRect();
    return { x: (e.clientX - r.left) * (foil.width / r.width), y: (e.clientY - r.top) * (foil.height / r.height) };
  }

  paintFoil();

  var reduce = window.matchMedia('(prefers-reduced-motion: reduce)').matches;
  var dragging = false;

  zone.addEventListener('pointerdown', function (e) {
    if (opened) return;
    root.classList.remove('is-demo');
    dragging = true;
    var p = pos(e);
    scratchAt(p.x, p.y);
    var ratio = clearedPixelRatio();
    updateMeter(ratio);
    autoPeelRemaining(ratio);
    if (foil.setPointerCapture) foil.setPointerCapture(e.pointerId);
  });
  zone.addEventListener('pointermove', function (e) {
    if (!dragging || opened) return;
    var p = pos(e);
    scratchAt(p.x, p.y);
    var ratio = clearedPixelRatio();
    updateMeter(ratio);
    autoPeelRemaining(ratio);
  });
  window.addEventListener('pointerup', function () { dragging = false; });

  revealBtn.addEventListener('click', function () {
    root.classList.remove('is-demo');
    openCard();
  });

  // 격자 미리보기 — 드래그 없이 같은 scratchAt·clearedPixelRatio 경로를 스케줄대로 호출한다
  var demoRand = seedRand(424012);
  var demoPath = [];
  (function buildDemoPath() {
    var n = 24;
    for (var i = 0; i < n; i += 1) {
      demoPath.push({
        t: 220 + i * 78,
        x: (foil.width * 0.16) + (i % 6) * (foil.width * 0.145) + (demoRand() - .5) * 8,
        y: (foil.height * 0.26) + Math.floor(i / 6) * (foil.height * 0.24) + (demoRand() - .5) * 8
      });
    }
  })();
  var DEMO_LOOP_MS = 3600;
  var demoStep = 0;

  function resetDemo() {
    opened = false;
    root.classList.remove('is-open');
    paintFoil();
    updateMeter(0);
    demoStep = 0;
  }

  function runDemo(tMod) {
    while (demoStep < demoPath.length && demoPath[demoStep].t <= tMod) {
      var p = demoPath[demoStep];
      scratchAt(p.x, p.y);
      demoStep += 1;
    }
    var ratio = clearedPixelRatio();
    updateMeter(ratio);
    autoPeelRemaining(ratio);
  }

  if (reduce) root.classList.remove('is-demo');
  var elapsed = 0;
  var lastTs = null;
  function tick(ts) {
    if (lastTs === null) lastTs = ts;
    var dt = Math.min(ts - lastTs, 48);
    lastTs = ts;
    if (!reduce && root.classList.contains('is-demo')) {
      elapsed += dt;
      var tMod = elapsed % DEMO_LOOP_MS;
      if (tMod < dt) resetDemo();
      runDemo(tMod);
    }
    requestAnimationFrame(tick);
  }
  updateMeter(0);
  requestAnimationFrame(tick);
})();

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

export default function ScratchCardRevealPixelThresholdAutopeel() {
  const rootRef = useRef<HTMLDivElement>(null);
  const zoneRef = useRef<HTMLDivElement>(null);
  const foilRef = useRef<HTMLCanvasElement>(null);
  const meterRef = useRef<HTMLDivElement>(null);
  const liveRef = useRef<HTMLParagraphElement>(null);
  const revealBtnRef = useRef<HTMLButtonElement>(null);

  useEffect(() => {
    const root = rootRef.current;
    const zone = zoneRef.current;
    const foil = foilRef.current;
    const meterFill = meterRef.current;
    const live = liveRef.current;
    const revealBtn = revealBtnRef.current;
    if (!root || !zone || !foil || !meterFill || !live || !revealBtn) return;
    const ctx = foil.getContext("2d");
    if (!ctx) return;

    const SCRATCH_REVEAL_THRESHOLD_PCT = 50;
    const SCRATCH_BRUSH_R = 15;
    let opened = false;

    function seedRand(seed: number) {
      let s = seed >>> 0;
      return function () { s = (s * 1664525 + 1013904223) >>> 0; return s / 4294967296; };
    }
    const foilRand = seedRand(424011);

    function paintFoil() {
      ctx!.globalCompositeOperation = "source-over";
      ctx!.clearRect(0, 0, foil!.width, foil!.height);
      const grad = ctx!.createLinearGradient(0, 0, foil!.width, foil!.height);
      grad.addColorStop(0, "#cfd3dd");
      grad.addColorStop(.5, "#eef0f5");
      grad.addColorStop(1, "#b9bdc9");
      ctx!.fillStyle = grad;
      ctx!.fillRect(0, 0, foil!.width, foil!.height);
      ctx!.strokeStyle = "rgba(23,20,26,.16)";
      ctx!.lineWidth = 1;
      for (let i = 0; i < 22; i += 1) {
        const x = foilRand() * foil!.width, y = foilRand() * foil!.height;
        ctx!.beginPath();
        ctx!.moveTo(x, y);
        ctx!.lineTo(x + (foilRand() * 22 - 11), y + (foilRand() * 8 - 4));
        ctx!.stroke();
      }
    }

    function scratchAt(x: number, y: number) {
      ctx!.globalCompositeOperation = "destination-out";
      ctx!.beginPath();
      ctx!.arc(x, y, SCRATCH_BRUSH_R, 0, Math.PI * 2);
      ctx!.fill();
    }

    function clearedPixelRatio() {
      const data = ctx!.getImageData(0, 0, foil!.width, foil!.height).data;
      let clear = 0;
      const total = data.length / 4;
      for (let i = 3; i < data.length; i += 4) { if (data[i] < 40) clear += 1; }
      return clear / total;
    }

    function updateMeter(ratio: number) {
      meterFill!.style.width = Math.round(ratio * 100) + "%";
    }

    function openCard() {
      if (opened) return;
      opened = true;
      ctx!.globalCompositeOperation = "destination-out";
      ctx!.fillRect(0, 0, foil!.width, foil!.height);
      updateMeter(1);
      root!.classList.add("is-open");
      live!.textContent = "20% 할인 쿠폰이 열렸어요";
    }

    function autoPeelRemaining(ratio: number) {
      if (ratio * 100 >= SCRATCH_REVEAL_THRESHOLD_PCT) openCard();
    }

    function pos(e: PointerEvent) {
      const r = foil!.getBoundingClientRect();
      return { x: (e.clientX - r.left) * (foil!.width / r.width), y: (e.clientY - r.top) * (foil!.height / r.height) };
    }

    paintFoil();

    const reduce = window.matchMedia("(prefers-reduced-motion: reduce)").matches;
    let dragging = false;

    function onDown(e: PointerEvent) {
      if (opened) return;
      root!.classList.remove("is-demo");
      dragging = true;
      const p = pos(e);
      scratchAt(p.x, p.y);
      const ratio = clearedPixelRatio();
      updateMeter(ratio);
      autoPeelRemaining(ratio);
      foil!.setPointerCapture?.(e.pointerId);
    }
    function onMove(e: PointerEvent) {
      if (!dragging || opened) return;
      const p = pos(e);
      scratchAt(p.x, p.y);
      const ratio = clearedPixelRatio();
      updateMeter(ratio);
      autoPeelRemaining(ratio);
    }
    function onUp() { dragging = false; }
    zone.addEventListener("pointerdown", onDown);
    zone.addEventListener("pointermove", onMove);
    window.addEventListener("pointerup", onUp);

    function onReveal() {
      root!.classList.remove("is-demo");
      openCard();
    }
    revealBtn.addEventListener("click", onReveal);

    const demoRand = seedRand(424012);
    type DemoPt = { t: number; x: number; y: number };
    const demoPath: DemoPt[] = [];
    for (let i = 0; i < 24; i += 1) {
      demoPath.push({
        t: 220 + i * 78,
        x: (foil.width * 0.16) + (i % 6) * (foil.width * 0.145) + (demoRand() - .5) * 8,
        y: (foil.height * 0.26) + Math.floor(i / 6) * (foil.height * 0.24) + (demoRand() - .5) * 8
      });
    }
    const DEMO_LOOP_MS = 3600;
    let demoStep = 0;

    function resetDemo() {
      opened = false;
      root!.classList.remove("is-open");
      paintFoil();
      updateMeter(0);
      demoStep = 0;
    }
    function runDemo(tMod: number) {
      while (demoStep < demoPath.length && demoPath[demoStep].t <= tMod) {
        const p = demoPath[demoStep];
        scratchAt(p.x, p.y);
        demoStep += 1;
      }
      const ratio = clearedPixelRatio();
      updateMeter(ratio);
      autoPeelRemaining(ratio);
    }

    if (reduce) root.classList.remove("is-demo");
    let elapsed = 0;
    let lastTs: number | null = null;
    let raf = 0;
    function tick(ts: number) {
      if (lastTs === null) lastTs = ts;
      const dt = Math.min(ts - lastTs, 48);
      lastTs = ts;
      if (!reduce && root!.classList.contains("is-demo")) {
        elapsed += dt;
        const tMod = elapsed % DEMO_LOOP_MS;
        if (tMod < dt) resetDemo();
        runDemo(tMod);
      }
      raf = requestAnimationFrame(tick);
    }
    updateMeter(0);
    raf = requestAnimationFrame(tick);

    return () => {
      cancelAnimationFrame(raf);
      zone.removeEventListener("pointerdown", onDown);
      zone.removeEventListener("pointermove", onMove);
      window.removeEventListener("pointerup", onUp);
      revealBtn.removeEventListener("click", onReveal);
    };
  }, []);

  return (
    <main className={styles.stage}>
      <div className={`${styles.scv} is-demo`} ref={rootRef}>
        <div className={styles.scv__card}>
          <p className={styles.scv__label}>스크래치 카드</p>
          <div className={styles.scv__zone} ref={zoneRef}>
            <div className={styles.scv__prize}>
              <p className={styles.scv__prizeTitle}>20% 할인 쿠폰</p>
              <p className={styles.scv__prizeSub}>긁어서 결과를 확인하세요</p>
            </div>
            <canvas className={styles.scv__foil} ref={foilRef} width={280} height={150} aria-hidden="true" />
          </div>
          <div className={styles.scv__meter} aria-hidden="true"><div className={styles.scv__meterFill} ref={meterRef} /></div>
          <button type="button" className={styles.scv__reveal} ref={revealBtnRef}>한 번에 보기</button>
          <p className={styles.scv__live} ref={liveRef} aria-live="polite"></p>
        </div>
      </div>
    </main>
  );
}