03Six filter presets

<main class="stage">
<div class="fp is-demo" id="fp">
  <div class="fp__frame">
    <canvas class="fp__view" id="view" width="320" height="200" role="img" aria-label="Preview photo, no filter"></canvas>
    <span class="fp__ghost" aria-hidden="true"></span>
  </div>
  <div class="fp__row" id="row">
    <span class="fp__ring" aria-hidden="true"></span>
    <button type="button" class="fp__p" data-f="none" aria-pressed="true"><span class="fp__sw fp__sw--a" aria-hidden="true"></span><span class="fp__name">Original</span></button>
    <button type="button" class="fp__p" data-f="grayscale(1) contrast(1.08)" aria-pressed="false"><span class="fp__sw fp__sw--b" aria-hidden="true"></span><span class="fp__name">Mono</span></button>
    <button type="button" class="fp__p" data-f="sepia(0.75) saturate(1.2)" aria-pressed="false"><span class="fp__sw fp__sw--c" aria-hidden="true"></span><span class="fp__name">Sepia</span></button>
    <button type="button" class="fp__p" data-f="contrast(1.3) saturate(1.35)" aria-pressed="false"><span class="fp__sw fp__sw--d" aria-hidden="true"></span><span class="fp__name">Vivid</span></button>
    <button type="button" class="fp__p" data-f="saturate(0.55) brightness(1.08)" aria-pressed="false"><span class="fp__sw fp__sw--e" aria-hidden="true"></span><span class="fp__name">Muted</span></button>
    <button type="button" class="fp__p" data-f="sepia(0.4) contrast(0.9) hue-rotate(-14deg)" aria-pressed="false"><span class="fp__sw fp__sw--f" aria-hidden="true"></span><span class="fp__name">Vintage</span></button>
  </div>
  <p class="fp__code">
    <code class="fp__real" id="code">filter: none;</code>
    <code class="fp__demo fp__demo--a" aria-hidden="true">filter: none;</code>
    <code class="fp__demo fp__demo--b" aria-hidden="true">filter: grayscale(1) contrast(1.08);</code>
    <code class="fp__demo fp__demo--c" aria-hidden="true">filter: sepia(0.75) saturate(1.2);</code>
    <code class="fp__demo fp__demo--d" aria-hidden="true">filter: contrast(1.3) saturate(1.35);</code>
    <code class="fp__demo fp__demo--e" aria-hidden="true">filter: saturate(0.55) brightness(1.08);</code>
    <code class="fp__demo fp__demo--f" aria-hidden="true">filter: sepia(0.4) contrast(0.9) hue-rotate(-14deg);</code>
  </p>
</div>
</main>

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

// 필터 프리셋 여섯 개 — 누르면 큰 사진과 아래 글자가 같이 바뀐다. 프리셋 값은 index.html 의 data-f 하나뿐이다.
// 격자 미리보기(.is-demo)는 유령 판의 filter 를 여섯 상태로 이어 돌린다. 이때만 함수 목록을
// grayscale sepia saturate contrast brightness hue-rotate 여섯 개로 통일해 적는다 —
// 함수 목록이 서로 다르면 브라우저가 보간을 포기하고 툭 끊기기 때문이다. 계산 결과는 프리셋과 같다.

$duration: $dur-loop;
$easing: $ease-out;
$color: $subject-ink;

@include stage($stage-yellow);

.fp { display: flex; flex-direction: column; align-items: center; gap: $sp-2; width: 100%; }
.fp__frame {
  position: relative; height: clamp(84px, 42vh, 148px); aspect-ratio: 16 / 10; max-width: 100%;
  border-radius: $r-sm; overflow: hidden; box-shadow: $shadow-raised;
}
.fp__view { display: block; width: 100%; height: 100%; }
.fp__ghost {
  display: none; position: absolute; inset: 0;
  background-image: var(--photo); background-size: cover;
}

.fp__row {
  position: relative; display: grid; grid-template-columns: repeat(6, 1fr);
  width: min(100%, 300px);
}
.fp__ring {
  position: absolute; top: 0; left: 0; width: calc(100% / 6); height: 100%;
  border: 2px solid $color; border-radius: $r-sm; pointer-events: none;
}
.fp__p {
  display: grid; justify-items: center; gap: $sp-1; width: 100%; cursor: pointer;
  padding: $sp-1; border: 0; background: transparent; color: $color;
  font-family: inherit; font-weight: 700;
}
.fp__p:focus-visible { outline: 3px solid $subject-blue; outline-offset: 2px; }
.fp__sw {
  width: 100%; height: 20px; border-radius: $r-xs;
  background-image: var(--photo); background-size: cover; background-position: center;
}
.fp__sw--b { filter: grayscale(1) contrast(1.08); }
.fp__sw--c { filter: sepia(0.75) saturate(1.2); }
.fp__sw--d { filter: contrast(1.3) saturate(1.35); }
.fp__sw--e { filter: saturate(0.55) brightness(1.08); }
.fp__sw--f { filter: sepia(0.4) contrast(0.9) hue-rotate(-14deg); }
.fp__name { font-size: clamp(8px, 2.2vw, 10px); line-height: 1.2; }

.fp__code {
  position: relative; margin: 0; width: min(100%, 300px); height: 14px;
  font-family: ui-monospace, "Consolas", monospace; font-size: clamp(8px, 2.1vw, 10px);
  color: rgba(23, 20, 26, .78); white-space: nowrap; overflow: hidden;
}
.fp__demo { display: none; position: absolute; left: 0; top: 0; }

// ── 미리보기 루프: 원본 → 흑백 → 세피아 → 선명 → 차분 → 빈티지 → 원본.
//    복귀는 88% 에 끝난다. 24장 표본의 마지막 장이 2초의 95.8% 지점이라 그 뒤는 안 찍힌다
.fp.is-demo .fp__view { visibility: hidden; }
.fp.is-demo .fp__ghost {
  display: block;
  animation-name: fpChain; animation-duration: $duration;
  animation-timing-function: $easing; animation-iteration-count: infinite;
}
@keyframes fpChain {
  0%, 10% { filter: grayscale(0) sepia(0) saturate(1) contrast(1) brightness(1) hue-rotate(0deg); }
  14%, 24% { filter: grayscale(1) sepia(0) saturate(1) contrast(1.08) brightness(1) hue-rotate(0deg); }
  28%, 38% { filter: grayscale(0) sepia(0.75) saturate(1.2) contrast(1) brightness(1) hue-rotate(0deg); }
  42%, 52% { filter: grayscale(0) sepia(0) saturate(1.35) contrast(1.3) brightness(1) hue-rotate(0deg); }
  56%, 66% { filter: grayscale(0) sepia(0) saturate(0.55) contrast(1) brightness(1.08) hue-rotate(0deg); }
  70%, 85% { filter: grayscale(0) sepia(0.4) saturate(1) contrast(0.9) brightness(1) hue-rotate(-14deg); }
  89%, 100% { filter: grayscale(0) sepia(0) saturate(1) contrast(1) brightness(1) hue-rotate(0deg); }
}
// 테두리는 글자와 **같은 순간에** 끊어야 한다 — 부드럽게 밀면 테두리가 먼저 도착한 프레임이
// poster 로 뽑혀 「선명 칸에 테두리, 아래는 세피아 값」 같은 어긋난 대표 이미지가 나온다 (실측)
.fp.is-demo .fp__ring {
  animation-name: fpRing; animation-duration: $duration;
  animation-timing-function: steps(1, end); animation-iteration-count: infinite;
}
@keyframes fpRing {
  0%, 11% { transform: translateX(0); }
  12%, 25% { transform: translateX(100%); }
  26%, 39% { transform: translateX(200%); }
  40%, 53% { transform: translateX(300%); }
  54%, 67% { transform: translateX(400%); }
  68%, 86% { transform: translateX(500%); }
  87%, 100% { transform: translateX(0); }
}

// 글자는 보간할 수 없으니 여섯 칸을 steps(1, end) 로 갈아 끼운다 — 반투명하게 겹치는 장면이 없다
.fp.is-demo .fp__real { color: transparent; }
.fp.is-demo .fp__demo {
  display: block;
  animation-duration: $duration;
  animation-timing-function: steps(1, end);
  animation-iteration-count: infinite;
}
.fp.is-demo .fp__demo--a { animation-name: fpTextA; }
.fp.is-demo .fp__demo--b { animation-name: fpTextB; }
.fp.is-demo .fp__demo--c { animation-name: fpTextC; }
.fp.is-demo .fp__demo--d { animation-name: fpTextD; }
.fp.is-demo .fp__demo--e { animation-name: fpTextE; }
.fp.is-demo .fp__demo--f { animation-name: fpTextF; }
@keyframes fpTextA { 0%, 11% { opacity: 1; } 12%, 86% { opacity: 0; } 87%, 100% { opacity: 1; } }
@keyframes fpTextB { 0%, 11% { opacity: 0; } 12%, 25% { opacity: 1; } 26%, 100% { opacity: 0; } }
@keyframes fpTextC { 0%, 25% { opacity: 0; } 26%, 39% { opacity: 1; } 40%, 100% { opacity: 0; } }
@keyframes fpTextD { 0%, 39% { opacity: 0; } 40%, 53% { opacity: 1; } 54%, 100% { opacity: 0; } }
@keyframes fpTextE { 0%, 53% { opacity: 0; } 54%, 67% { opacity: 1; } 68%, 100% { opacity: 0; } }
@keyframes fpTextF { 0%, 67% { opacity: 0; } 68%, 86% { opacity: 1; } 87%, 100% { opacity: 0; } }

@media (max-width: 340px) {
  .fp { gap: $sp-1; }
  .fp__sw { height: 16px; }
}

@media (prefers-reduced-motion: reduce) {
  .fp.is-demo .fp__ghost,
  .fp.is-demo .fp__ring,
  .fp.is-demo .fp__demo { animation: none !important; }
  // 움직임 없이 세피아를 고른 상태로 세운다
  .fp.is-demo .fp__ghost { filter: grayscale(0) sepia(0.75) saturate(1.2) contrast(1) brightness(1) hue-rotate(0deg) !important; }
  .fp.is-demo .fp__ring { transform: translateX(200%) !important; }
  .fp.is-demo .fp__demo--a,
  .fp.is-demo .fp__demo--b,
  .fp.is-demo .fp__demo--d,
  .fp.is-demo .fp__demo--e,
  .fp.is-demo .fp__demo--f { opacity: 0 !important; }
  .fp.is-demo .fp__demo--c { opacity: 1 !important; }
}

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

.stage {
  box-sizing: border-box;
  min-height: 100vh;
  display: grid;
  place-items: center;
  margin: 0;
  background: #ffd23f;
  font-family: -apple-system, "Segoe UI", "Noto Sans KR", sans-serif;
  padding: clamp(8px, 4vw, 24px);
}

.fp {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 8px;
  width: 100%;
}

.fp__frame {
  position: relative;
  height: clamp(84px, 42vh, 148px);
  aspect-ratio: 16/10;
  max-width: 100%;
  border-radius: 8px;
  overflow: hidden;
  box-shadow: 0 14px 24px rgba(23, 20, 26, 0.32);
}

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

.fp__ghost {
  display: none;
  position: absolute;
  inset: 0;
  background-image: var(--photo);
  background-size: cover;
}

.fp__row {
  position: relative;
  display: grid;
  grid-template-columns: repeat(6, 1fr);
  width: min(100%, 300px);
}

.fp__ring {
  position: absolute;
  top: 0;
  left: 0;
  width: 16.6666666667%;
  height: 100%;
  border: 2px solid #17141a;
  border-radius: 8px;
  pointer-events: none;
}

.fp__p {
  display: grid;
  justify-items: center;
  gap: 4px;
  width: 100%;
  cursor: pointer;
  padding: 4px;
  border: 0;
  background: transparent;
  color: #17141a;
  font-family: inherit;
  font-weight: 700;
}

.fp__p:focus-visible {
  outline: 3px solid #2f6df6;
  outline-offset: 2px;
}

.fp__sw {
  width: 100%;
  height: 20px;
  border-radius: 4px;
  background-image: var(--photo);
  background-size: cover;
  background-position: center;
}

.fp__sw--b {
  filter: grayscale(1) contrast(1.08);
}

.fp__sw--c {
  filter: sepia(0.75) saturate(1.2);
}

.fp__sw--d {
  filter: contrast(1.3) saturate(1.35);
}

.fp__sw--e {
  filter: saturate(0.55) brightness(1.08);
}

.fp__sw--f {
  filter: sepia(0.4) contrast(0.9) hue-rotate(-14deg);
}

.fp__name {
  font-size: clamp(8px, 2.2vw, 10px);
  line-height: 1.2;
}

.fp__code {
  position: relative;
  margin: 0;
  width: min(100%, 300px);
  height: 14px;
  font-family: ui-monospace, "Consolas", monospace;
  font-size: clamp(8px, 2.1vw, 10px);
  color: rgba(23, 20, 26, 0.78);
  white-space: nowrap;
  overflow: hidden;
}

.fp__demo {
  display: none;
  position: absolute;
  left: 0;
  top: 0;
}

.fp.is-demo .fp__view {
  visibility: hidden;
}

.fp.is-demo .fp__ghost {
  display: block;
  animation-name: fpChain;
  animation-duration: 2s;
  animation-timing-function: ease-out;
  animation-iteration-count: infinite;
}

@keyframes fpChain {
  0%, 10% {
    filter: grayscale(0) sepia(0) saturate(1) contrast(1) brightness(1) hue-rotate(0deg);
  }
  14%, 24% {
    filter: grayscale(1) sepia(0) saturate(1) contrast(1.08) brightness(1) hue-rotate(0deg);
  }
  28%, 38% {
    filter: grayscale(0) sepia(0.75) saturate(1.2) contrast(1) brightness(1) hue-rotate(0deg);
  }
  42%, 52% {
    filter: grayscale(0) sepia(0) saturate(1.35) contrast(1.3) brightness(1) hue-rotate(0deg);
  }
  56%, 66% {
    filter: grayscale(0) sepia(0) saturate(0.55) contrast(1) brightness(1.08) hue-rotate(0deg);
  }
  70%, 85% {
    filter: grayscale(0) sepia(0.4) saturate(1) contrast(0.9) brightness(1) hue-rotate(-14deg);
  }
  89%, 100% {
    filter: grayscale(0) sepia(0) saturate(1) contrast(1) brightness(1) hue-rotate(0deg);
  }
}
.fp.is-demo .fp__ring {
  animation-name: fpRing;
  animation-duration: 2s;
  animation-timing-function: steps(1, end);
  animation-iteration-count: infinite;
}

@keyframes fpRing {
  0%, 11% {
    transform: translateX(0);
  }
  12%, 25% {
    transform: translateX(100%);
  }
  26%, 39% {
    transform: translateX(200%);
  }
  40%, 53% {
    transform: translateX(300%);
  }
  54%, 67% {
    transform: translateX(400%);
  }
  68%, 86% {
    transform: translateX(500%);
  }
  87%, 100% {
    transform: translateX(0);
  }
}
.fp.is-demo .fp__real {
  color: transparent;
}

.fp.is-demo .fp__demo {
  display: block;
  animation-duration: 2s;
  animation-timing-function: steps(1, end);
  animation-iteration-count: infinite;
}

.fp.is-demo .fp__demo--a {
  animation-name: fpTextA;
}

.fp.is-demo .fp__demo--b {
  animation-name: fpTextB;
}

.fp.is-demo .fp__demo--c {
  animation-name: fpTextC;
}

.fp.is-demo .fp__demo--d {
  animation-name: fpTextD;
}

.fp.is-demo .fp__demo--e {
  animation-name: fpTextE;
}

.fp.is-demo .fp__demo--f {
  animation-name: fpTextF;
}

@keyframes fpTextA {
  0%, 11% {
    opacity: 1;
  }
  12%, 86% {
    opacity: 0;
  }
  87%, 100% {
    opacity: 1;
  }
}
@keyframes fpTextB {
  0%, 11% {
    opacity: 0;
  }
  12%, 25% {
    opacity: 1;
  }
  26%, 100% {
    opacity: 0;
  }
}
@keyframes fpTextC {
  0%, 25% {
    opacity: 0;
  }
  26%, 39% {
    opacity: 1;
  }
  40%, 100% {
    opacity: 0;
  }
}
@keyframes fpTextD {
  0%, 39% {
    opacity: 0;
  }
  40%, 53% {
    opacity: 1;
  }
  54%, 100% {
    opacity: 0;
  }
}
@keyframes fpTextE {
  0%, 53% {
    opacity: 0;
  }
  54%, 67% {
    opacity: 1;
  }
  68%, 100% {
    opacity: 0;
  }
}
@keyframes fpTextF {
  0%, 67% {
    opacity: 0;
  }
  68%, 86% {
    opacity: 1;
  }
  87%, 100% {
    opacity: 0;
  }
}
@media (max-width: 340px) {
  .fp {
    gap: 4px;
  }
  .fp__sw {
    height: 16px;
  }
}
@media (prefers-reduced-motion: reduce) {
  .fp.is-demo .fp__ghost,
  .fp.is-demo .fp__ring,
  .fp.is-demo .fp__demo {
    animation: none !important;
  }
  .fp.is-demo .fp__ghost {
    filter: grayscale(0) sepia(0.75) saturate(1.2) contrast(1) brightness(1) hue-rotate(0deg) !important;
  }
  .fp.is-demo .fp__ring {
    transform: translateX(200%) !important;
  }
  .fp.is-demo .fp__demo--a,
  .fp.is-demo .fp__demo--b,
  .fp.is-demo .fp__demo--d,
  .fp.is-demo .fp__demo--e,
  .fp.is-demo .fp__demo--f {
    opacity: 0 !important;
  }
  .fp.is-demo .fp__demo--c {
    opacity: 1 !important;
  }
}

var fp = document.getElementById('fp');
var view = document.getElementById('view');
var code = document.getElementById('code');
var ring = document.querySelector('.fp__ring');
var presets = document.querySelectorAll('.fp__p');
var VIEW_LABEL = 'Preview photo, filter %n';

// 가짜 사진 — 외부 파일 없이 그라디언트와 도형으로 합성한다. 필터·히스토그램이 보이도록 대비를 세게 준다
function paintPhoto(c, w, h) {
  var sky = c.createLinearGradient(0, 0, 0, h);
  sky.addColorStop(0, '#2f6df6'); sky.addColorStop(0.55, '#ff9ebb'); sky.addColorStop(1, '#ffd23f');
  c.fillStyle = sky; c.fillRect(0, 0, w, h);
  c.fillStyle = '#fff7e6';
  c.beginPath(); c.arc(w * 0.74, h * 0.28, h * 0.13, 0, Math.PI * 2); c.fill();
  // 곧은 수평선 하나 — 기울기 보정이 눈에 보이려면 비교할 직선이 있어야 한다
  c.fillStyle = 'rgba(23, 20, 26, 0.5)'; c.fillRect(0, Math.round(h * 0.66), w, 2);
  c.fillStyle = '#17141a';
  c.beginPath(); c.moveTo(0, h); c.lineTo(w * 0.34, h * 0.36); c.lineTo(w * 0.62, h); c.closePath(); c.fill();
  c.fillStyle = '#c2361a';
  c.beginPath(); c.moveTo(w * 0.46, h); c.lineTo(w * 0.78, h * 0.52); c.lineTo(w, h); c.closePath(); c.fill();
  for (var i = 0; i < 6; i++) { c.fillStyle = i % 2 ? '#fff7e6' : '#17141a'; c.fillRect(w * (0.08 + i * 0.07), h * (0.14 + (i % 3) * 0.06), 7, 7); }
}

function pick(index) {
  var el = presets[index], chain = el.getAttribute('data-f');
  fp.classList.remove('is-demo');
  for (var i = 0; i < presets.length; i++) { presets[i].setAttribute('aria-pressed', i === index ? 'true' : 'false'); }
  // 사진에는 CSS filter 를 unchanged 걸고, 같은 문자열을 아래 칸에 글자로 내보낸다
  view.style.filter = chain;
  code.textContent = 'filter: ' + chain + ';';
  ring.style.transform = 'translateX(' + index * 100 + '%)';
  view.setAttribute('aria-label', VIEW_LABEL.replace('%n', el.querySelector('.fp__name').textContent));
}

for (var i = 0; i < presets.length; i++) {
  (function (index) { presets[index].addEventListener('click', function () { pick(index); }); })(i);
}

paintPhoto(view.getContext('2d'), view.width, view.height);
document.documentElement.style.setProperty('--photo', 'url(' + view.toDataURL() + ')');

// FilterPresets — vanilla 판(run/295/demo/03-image-edit-filter-presets/index.html) 의 React 포트.
// 프리셋 여섯 개의 값은 PRESETS 배열 하나뿐이다 — 사진에 거는 CSS filter 와 아래 칸에 찍는 글자가 같은 문자열이다.
// 누른 칸은 aria-pressed 로 알리고, 테두리는 인덱스 × 100% 만큼 옆으로 민다. 값·수치는 vanilla 와 같다.
import { useEffect, useRef, useState } from "react";
import type { CSSProperties } from "react";
import styles from "./FilterPresets.module.scss";

export type FilterPresetsProps = {
  duration?: number;
  easing?: string;
  color?: string;
};

type Vars = CSSProperties & {
  "--duration"?: string;
  "--easing"?: string;
  "--color"?: string;
  "--photo"?: string;
};
type Preset = { name: string; chain: string; sw: string };

const VIEW_LABEL = "미리보기 사진, 필터 %n";
// 첫 화면의 대체텍스트는 통째로 사전에 든 문자열이다 — 「없음」만 따로 떼면 언어팩이 그 조각을 못 바꾼다
const VIEW_LABEL_NONE = "미리보기 사진, 필터 없음";
const VIEW_W = 320;
const VIEW_H = 200;

const PRESETS: Preset[] = [
  { name: "원본", chain: "none", sw: "swA" },
  { name: "흑백", chain: "grayscale(1) contrast(1.08)", sw: "swB" },
  { name: "세피아", chain: "sepia(0.75) saturate(1.2)", sw: "swC" },
  { name: "선명", chain: "contrast(1.3) saturate(1.35)", sw: "swD" },
  { name: "차분", chain: "saturate(0.55) brightness(1.08)", sw: "swE" },
  { name: "빈티지", chain: "sepia(0.4) contrast(0.9) hue-rotate(-14deg)", sw: "swF" },
];

// 가짜 사진 — 외부 파일 없이 그라디언트와 도형으로 합성한다. 필터·히스토그램이 보이도록 대비를 세게 준다
function paintPhoto(c: CanvasRenderingContext2D, w: number, h: number): void {
  const sky = c.createLinearGradient(0, 0, 0, h);
  sky.addColorStop(0, "#2f6df6"); sky.addColorStop(0.55, "#ff9ebb"); sky.addColorStop(1, "#ffd23f");
  c.fillStyle = sky; c.fillRect(0, 0, w, h);
  c.fillStyle = "#fff7e6";
  c.beginPath(); c.arc(w * 0.74, h * 0.28, h * 0.13, 0, Math.PI * 2); c.fill();
  // 곧은 수평선 하나 — 기울기 보정이 눈에 보이려면 비교할 직선이 있어야 한다
  c.fillStyle = "rgba(23, 20, 26, 0.5)"; c.fillRect(0, Math.round(h * 0.66), w, 2);
  c.fillStyle = "#17141a";
  c.beginPath(); c.moveTo(0, h); c.lineTo(w * 0.34, h * 0.36); c.lineTo(w * 0.62, h); c.closePath(); c.fill();
  c.fillStyle = "#c2361a";
  c.beginPath(); c.moveTo(w * 0.46, h); c.lineTo(w * 0.78, h * 0.52); c.lineTo(w, h); c.closePath(); c.fill();
  for (let i = 0; i < 6; i++) { c.fillStyle = i % 2 ? "#fff7e6" : "#17141a"; c.fillRect(w * (0.08 + i * 0.07), h * (0.14 + (i % 3) * 0.06), 7, 7); }
}

export default function FilterPresets({
  duration = 2000,
  easing = "ease-out",
  color = "#17141a",
}: FilterPresetsProps) {
  const viewRef = useRef<HTMLCanvasElement | null>(null);
  const [picked, setPicked] = useState(-1);
  const [demo, setDemo] = useState(true);
  const [photo, setPhoto] = useState("");
  const vars: Vars = { "--duration": `${duration}ms`, "--easing": easing, "--color": color };
  if (photo) vars["--photo"] = `url(${photo})`;

  // 아직 아무것도 안 누른 첫 화면은 원본 그대로다 — 그때의 대체텍스트만 「필터 없음」이다
  const index = picked < 0 ? 0 : picked;
  const chain = PRESETS[index].chain;
  const label = picked < 0 ? VIEW_LABEL_NONE : VIEW_LABEL.replace("%n", PRESETS[index].name);

  useEffect(() => {
    const view = viewRef.current;
    if (!view) return;
    const ctx = view.getContext("2d");
    if (!ctx) return;
    paintPhoto(ctx, view.width, view.height);
    setPhoto(view.toDataURL());
  }, []);

  // 사진에는 CSS filter 를 그대로 걸고, 같은 문자열을 아래 칸에 글자로 내보낸다
  function pick(next: number): void {
    setDemo(false);
    setPicked(next);
  }

  const cls = [styles.root, demo ? styles.isDemo : ""].filter(Boolean).join(" ");
  return (
    <main className={styles.stage}>
      <div className={cls} style={vars}>
        <div className={styles.frame}>
          <canvas className={styles.view} ref={viewRef} width={VIEW_W} height={VIEW_H} role="img" aria-label={label} style={{ filter: chain }}></canvas>
          <span className={styles.ghost} aria-hidden="true"></span>
        </div>
        <div className={styles.row}>
          <span className={styles.ring} style={{ transform: `translateX(${index * 100}%)` }} aria-hidden="true"></span>
          {PRESETS.map((preset, i) => (
            <button
              key={preset.name}
              type="button"
              className={styles.preset}
              aria-pressed={picked < 0 ? i === 0 : i === picked}
              onClick={() => pick(i)}
            >
              <span className={[styles.sw, styles[preset.sw]].filter(Boolean).join(" ")} aria-hidden="true"></span>
              <span className={styles.name}>{preset.name}</span>
            </button>
          ))}
        </div>
        <p className={styles.code}>
          <code className={styles.real}>{`filter: ${chain};`}</code>
          <code className={`${styles.codeDemo} ${styles.codeA}`} aria-hidden="true">filter: none;</code>
          <code className={`${styles.codeDemo} ${styles.codeB}`} aria-hidden="true">filter: grayscale(1) contrast(1.08);</code>
          <code className={`${styles.codeDemo} ${styles.codeC}`} aria-hidden="true">filter: sepia(0.75) saturate(1.2);</code>
          <code className={`${styles.codeDemo} ${styles.codeD}`} aria-hidden="true">filter: contrast(1.3) saturate(1.35);</code>
          <code className={`${styles.codeDemo} ${styles.codeE}`} aria-hidden="true">filter: saturate(0.55) brightness(1.08);</code>
          <code className={`${styles.codeDemo} ${styles.codeF}`} aria-hidden="true">filter: sepia(0.4) contrast(0.9) hue-rotate(-14deg);</code>
        </p>
      </div>
    </main>
  );
}