index.html

<!DOCTYPE html>
<html lang="ja">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>HTML to Image Playground</title>
  <style>
    :root {
      --bg: #f7f7f5;
      --panel: #ffffff;
      --border: #d9d9d4;
      --text: #1e1e1c;
      --muted: #6a6a62;
      --accent: #0f766e;
      --danger: #b91c1c;
    }

    * {
      box-sizing: border-box;
    }

    body {
      margin: 0;
      background: var(--bg);
      color: var(--text);
      font-family: "Hiragino Sans", "Yu Gothic", sans-serif;
    }

    main {
      width: min(1120px, calc(100vw - 32px));
      margin: 24px auto 40px;
      display: grid;
      gap: 16px;
    }

    .panel {
      background: var(--panel);
      border: 1px solid var(--border);
      border-radius: 16px;
      padding: 16px;
    }

    .warning-bar {
      display: none;
      padding: 12px 16px;
      background: #b91c1c;
      color: #fff;
      border-radius: 12px;
      font-weight: 700;
    }

    .warning-bar.is-visible {
      display: block;
    }

    h1,
    h2 {
      margin: 0;
    }

    h1 {
      font-size: 1.8rem;
    }

    h2 {
      font-size: 1rem;
    }

    p {
      margin: 8px 0 0;
      color: var(--muted);
      line-height: 1.6;
    }

    .controls {
      display: grid;
      gap: 12px;
    }

    label {
      display: grid;
      gap: 6px;
      color: var(--muted);
      font-size: 0.92rem;
    }

    textarea,
    input,
    select {
      width: 100%;
      border: 1px solid var(--border);
      border-radius: 12px;
      background: #fff;
      color: var(--text);
      font: inherit;
    }

    textarea {
      min-height: 280px;
      padding: 14px;
      line-height: 1.6;
      resize: vertical;
    }

    .css-input {
      min-height: 96px;
    }

    input,
    select {
      padding: 10px 12px;
    }

    .row {
      display: grid;
      grid-template-columns: repeat(2, minmax(0, 1fr));
      gap: 12px;
    }

    .actions {
      display: flex;
      flex-wrap: wrap;
      gap: 10px;
      align-items: center;
    }

    button {
      appearance: none;
      border: 0;
      border-radius: 999px;
      padding: 10px 16px;
      font: inherit;
      font-weight: 700;
      cursor: pointer;
    }

    button:disabled {
      opacity: 0.45;
      cursor: wait;
    }

    .primary {
      background: var(--accent);
      color: #fff;
    }

    .secondary {
      background: #ededea;
      color: var(--text);
    }

    .status {
      min-height: 1.4em;
      color: var(--muted);
      font-size: 0.95rem;
    }

    .status.error {
      color: var(--danger);
    }

    .preview-grid {
      display: grid;
      grid-template-columns: repeat(2, minmax(0, 1fr));
      gap: 16px;
    }

    .preview-card {
      display: grid;
      gap: 10px;
    }

    .preview-stage {
      display: flex;
      align-items: flex-start;
      border: 1px solid var(--border);
      border-radius: 14px;
      padding: 12px;
      background:
        linear-gradient(45deg, rgba(0, 0, 0, 0.03) 25%, transparent 25%),
        linear-gradient(-45deg, rgba(0, 0, 0, 0.03) 25%, transparent 25%),
        linear-gradient(45deg, transparent 75%, rgba(0, 0, 0, 0.03) 75%),
        linear-gradient(-45deg, transparent 75%, rgba(0, 0, 0, 0.03) 75%);
      background-size: 20px 20px;
      background-position: 0 0, 0 10px, 10px -10px, -10px 0;
      overflow: auto;
    }

    .preview-shell {
      display: inline-block;
      transform-origin: top left;
    }

    .preview-surface,
    .image-output {
      display: block;
      width: 100%;
      max-width: 100%;
      background: #fff;
      overflow: hidden;
    }

    .preview-surface {
      min-height: 120px;
    }

    .preview-surface > * {
      max-width: 100%;
    }

    .image-output {
      object-fit: contain;
      vertical-align: top;
    }

    .hidden-canvas {
      position: absolute;
      width: 1px;
      height: 1px;
      opacity: 0;
      pointer-events: none;
    }

    .measure-root {
      position: absolute;
      left: -99999px;
      top: 0;
      visibility: hidden;
      pointer-events: none;
    }

    .measure-surface {
      display: block;
      overflow: visible;
    }

    @media (max-width: 900px) {
      .row,
      .preview-grid {
        grid-template-columns: 1fr;
      }
    }
  </style>
</head>
<body>
  <main>
    <div id="safariWarning" class="warning-bar">
      Safari には対応していません。Chrome 系ブラウザで開いてください。
    </div>

    <section class="panel">
      <h1>HTML to Image</h1>
      <p>HTML を入力すると、そのままの HTML プレビューと画像化した結果を並べて確認できます。</p>
    </section>

    <section class="panel controls">
      <label for="sampleSelect">
        Sample
        <select id="sampleSelect">
          <option value="simple">Simple</option>
          <option value="game_notice_stable">Game Notice / Stable</option>
          <option value="game_notice_stress">Game Notice / Stress</option>
          <option value="news_article">News Article</option>
        </select>
      </label>

      <label for="htmlInput">
        HTML
        <textarea id="htmlInput" spellcheck="false"><div style="width:100%;height:100%;display:flex;align-items:center;justify-content:center;background:linear-gradient(135deg,#0f766e 0%,#f59e0b 100%);color:white;font-family:'Hiragino Sans','Yu Gothic',sans-serif;">
  <div style="padding:36px 44px;border:1px solid rgba(255,255,255,.35);border-radius:28px;background:rgba(255,255,255,.12);box-shadow:0 18px 50px rgba(0,0,0,.18);text-align:center;">
    <div style="font-size:14px;letter-spacing:.24em;text-transform:uppercase;opacity:.85;">Client-side only</div>
    <h1 style="margin:12px 0 8px;font-size:44px;line-height:1;">HTML → Image</h1>
    <p style="margin:0;font-size:18px;opacity:.92;">HTML preview と image preview を並べて確認</p>
  </div>
</div></textarea>
      </label>

      <label for="cssInput">
        CSS
        <textarea
          id="cssInput"
          class="css-input"
          spellcheck="false"
          placeholder=".card { color: red; }"
        >.external-card {
  padding: 40px;
  background: linear-gradient(135deg, #1d4ed8 0%, #0f766e 100%);
  color: #ffffff;
  font-family: "Hiragino Sans", "Yu Gothic", sans-serif;
}

.external-card__panel {
  padding: 28px 32px;
  border-radius: 24px;
  background: rgba(255, 255, 255, 0.12);
  border: 1px solid rgba(255, 255, 255, 0.2);
}

.external-card__eyebrow {
  font-size: 14px;
  letter-spacing: 0.24em;
  text-transform: uppercase;
  opacity: 0.8;
}

.external-card__title {
  margin: 12px 0 8px;
  font-size: 48px;
  line-height: 1.05;
}

.external-card__body {
  margin: 0;
  font-size: 20px;
  line-height: 1.6;
}</textarea>
      </label>

      <div class="row">
        <label for="widthInput">
          Width
          <input id="widthInput" type="number" min="1" value="1200">
        </label>
        <label for="backgroundInput">
          Background
          <input id="backgroundInput" type="text" value="#ffffff">
        </label>
      </div>

      <div class="actions">
        <button class="primary" id="renderButton">更新する</button>
        <button class="secondary" id="sampleButton">サンプルを再読込</button>
        <button class="secondary" id="downloadButton" disabled>PNG を保存</button>
      </div>

      <div id="status" class="status">準備完了</div>
    </section>

    <section class="panel preview-grid">
      <article class="preview-card">
        <h2>HTML Preview</h2>
        <div class="preview-stage">
          <div id="htmlPreviewShell" class="preview-shell">
            <div id="htmlPreview" class="preview-surface"></div>
          </div>
        </div>
      </article>

      <article class="preview-card">
        <h2>Image Preview</h2>
        <div class="preview-stage">
          <img id="pngOutput" class="image-output" alt="生成されたPNGプレビュー">
        </div>
      </article>
    </section>
  </main>

  <canvas id="previewCanvas" class="hidden-canvas" width="1200" height="630"></canvas>
  <a id="downloadLink" hidden>download</a>
  <div class="measure-root" aria-hidden="true">
    <div id="measureSurface" class="measure-surface"></div>
  </div>

  <script src="./script.js"></script>
</body>
</html>