One-File-Tools/tools/responsive-image-simulator.html at main · praveenscience/One-File-Tools · GitHub

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<!--
Responsive Image Simulator
Single-file client-side tool to preview a responsive image (srcset/sizes) at
common device breakpoints and see exactly which source the browser selects
and at what rendered width.
Built for One File Tools.
-->
<!doctype html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Responsive Image Simulator - One File Tools</title>
    <meta name="description" content="Preview a srcset/sizes image at common device breakpoints and see which source the browser selects." />
    <link rel="preconnect" href="https://fonts.googleapis.com" />
    <link rel="preconnect" href="https://fonts.gstatic.com" crossorigin />
    <link href="https://fonts.googleapis.com/css2?family=Space+Grotesk:wght@600;700&family=Inter:wght@400;500;600&family=JetBrains+Mono:wght@400;500;600&display=swap" rel="stylesheet" />

    <style>
      :root {
        --bg: #030712;
        --grid-line: #111827;
        --panel: rgba(17, 24, 39, 0.7);
        --panel-border: #1f2937;
        --accent: #fb923c;
        --accent-hover: #f97316;
        --accent-glow: rgba(251, 146, 60, 0.15);
        --text: #f9fafb;
        --text-muted: #9ca3af;
        --text-dim: #4b5563;
        --radius-sm: 12px;
        --radius-md: 20px;
        --font-sans: "Inter", system-ui, sans-serif;
        --font-mono: "JetBrains Mono", monospace;
        --font-display: "Space Grotesk", sans-serif;
        --color-weak: #ef4444;
      }

      * {
        margin: 0;
        padding: 0;
        box-sizing: border-box;
      }

      body {
        font-family: var(--font-sans);
        background-color: var(--bg);
        background-image: linear-gradient(var(--grid-line) 1px, transparent 1px), linear-gradient(90deg, var(--grid-line) 1px, transparent 1px);
        background-size: 32px 32px;
        color: var(--text);
        padding: 48px 20px 80px;
        min-height: 100vh;
        display: flex;
        justify-content: center;
      }

      .app {
        width: 100%;
        max-width: 960px;
      }

      .hero {
        text-align: center;
        margin-bottom: 32px;
      }

      .eyebrow {
        font-family: var(--font-mono);
        font-size: 12px;
        letter-spacing: 0.2em;
        color: var(--accent);
        text-transform: uppercase;
        margin-bottom: 12px;
        font-weight: 500;
      }

      .wordmark {
        font-family: var(--font-display);
        font-weight: 700;
        font-size: clamp(26px, 5vw, 38px);
        letter-spacing: -0.02em;
        margin-bottom: 12px;
      }

      .tagline {
        color: var(--text-muted);
        font-size: 15px;
        line-height: 1.5;
        max-width: 600px;
        margin: 0 auto;
      }

      .studio {
        background: var(--panel);
        backdrop-filter: blur(20px);
        border: 1px solid var(--panel-border);
        border-radius: var(--radius-md);
        padding: 28px;
        box-shadow: 0 24px 48px -12px rgba(0, 0, 0, 0.5);
        margin-bottom: 24px;
      }

      .section-label {
        font-family: var(--font-mono);
        font-size: 12px;
        font-weight: 600;
        color: var(--text-muted);
        text-transform: uppercase;
        letter-spacing: 0.1em;
        display: block;
        margin-bottom: 14px;
      }

      .field {
        display: flex;
        flex-direction: column;
        gap: 6px;
        margin-bottom: 14px;
      }

      .field label {
        font-family: var(--font-mono);
        font-size: 11px;
        color: var(--text-dim);
        text-transform: uppercase;
        letter-spacing: 0.05em;
      }

      .field input,
      .field textarea {
        background: rgba(17, 24, 39, 0.8);
        border: 1px solid var(--panel-border);
        border-radius: 8px;
        color: var(--text);
        font-family: var(--font-mono);
        font-size: 14px;
        padding: 10px 12px;
        width: 100%;
      }

      .field textarea {
        resize: vertical;
        min-height: 70px;
        line-height: 1.5;
      }

      .field input:focus,
      .field textarea:focus {
        outline: none;
        border-color: var(--accent);
        box-shadow: 0 0 0 3px var(--accent-glow);
      }

      .field-error {
        font-size: 12px;
        color: var(--color-weak);
        min-height: 14px;
      }

      .breakpoint-tabs {
        display: flex;
        gap: 6px;
        flex-wrap: wrap;
        margin-bottom: 16px;
      }

      .bp-tab {
        background: rgba(31, 41, 55, 0.5);
        border: 1px solid var(--panel-border);
        color: var(--text-muted);
        border-radius: 8px;
        padding: 8px 14px;
        font-family: var(--font-mono);
        font-size: 12px;
        cursor: pointer;
      }

      .bp-tab.active {
        background: var(--accent);
        color: #030712;
        border-color: var(--accent);
        font-weight: 700;
      }

      .bp-tab:hover:not(.active) {
        background: rgba(55, 65, 81, 0.7);
      }

      .bp-tab:focus-visible {
        outline: 2px solid var(--accent);
        outline-offset: 2px;
      }

      .device-frame {
        background: rgba(3, 7, 18, 0.5);
        border: 1px solid var(--panel-border);
        border-radius: var(--radius-sm);
        padding: 16px;
        overflow-x: auto;
      }

      .viewport-shell {
        margin: 0 auto;
        border: 2px solid var(--panel-border);
        border-radius: 10px;
        overflow: hidden;
        transition: width 0.3s ease;
        background: #000;
      }

      .viewport-shell img {
        display: block;
        width: 100%;
        height: auto;
      }

      .viewport-meta {
        text-align: center;
        margin-top: 10px;
        font-family: var(--font-mono);
        font-size: 12px;
        color: var(--text-muted);
      }

      .info-grid {
        display: grid;
        grid-template-columns: repeat(auto-fit, minmax(140px, 1fr));
        gap: 10px;
        margin-top: 16px;
      }

      .info-card {
        background: rgba(3, 7, 18, 0.5);
        border: 1px solid var(--panel-border);
        border-radius: var(--radius-sm);
        padding: 12px 14px;
      }

      .info-card .label {
        font-family: var(--font-mono);
        font-size: 11px;
        color: var(--text-dim);
        text-transform: uppercase;
        letter-spacing: 0.05em;
        margin-bottom: 4px;
      }

      .info-card .value {
        font-family: var(--font-mono);
        font-size: 15px;
        color: var(--text);
        word-break: break-all;
      }

      .note {
        margin-top: 16px;
        font-size: 13px;
        color: var(--text-muted);
        line-height: 1.6;
        background: rgba(251, 146, 60, 0.07);
        border: 1px solid rgba(251, 146, 60, 0.25);
        border-radius: var(--radius-sm);
        padding: 12px 14px;
      }

      .note code {
        color: var(--text);
        font-family: var(--font-mono);
      }

      .footer-note {
        text-align: center;
        color: var(--text-dim);
        font-size: 13px;
        margin-top: 8px;
      }

      .footer-note a {
        color: var(--text-muted);
      }

      @media (max-width: 640px) {
        .studio {
          padding: 20px;
        }
      }
    </style>
  </head>
  <body>
    <div class="app">
      <header class="hero">
        <div class="eyebrow">Image Tools</div>
        <h1 class="wordmark">Responsive Image Simulator</h1>
        <p class="tagline">Preview a <code>srcset</code>/<code>sizes</code> image at common device breakpoints, and see exactly which source the browser would pick and at what rendered width.</p>
      </header>

      <main class="studio">
        <span class="section-label">Image markup</span>
        <div class="field">
          <label for="srcsetInput">srcset</label>
          <textarea id="srcsetInput" spellcheck="false">
https://picsum.photos/id/1015/400/300 400w,
https://picsum.photos/id/1015/800/600 800w,
https://picsum.photos/id/1015/1200/900 1200w,
https://picsum.photos/id/1015/1600/1200 1600w</textarea>
          <div class="field-error" id="srcsetError"></div>
        </div>
        <div class="field">
          <label for="sizesInput">sizes</label>
          <input type="text" id="sizesInput" value="(max-width: 600px) 100vw, (max-width: 1024px) 50vw, 33vw" spellcheck="false" />
        </div>
        <div class="field">
          <label for="fallbackInput">Fallback src (for browsers without srcset support)</label>
          <input type="text" id="fallbackInput" value="https://picsum.photos/id/1015/800/600" spellcheck="false" />
        </div>
      </main>

      <main class="studio">
        <span class="section-label">Simulated viewport</span>
        <div class="breakpoint-tabs" id="breakpointTabs"></div>

        <div class="device-frame">
          <div class="viewport-shell" id="viewportShell">
            <img id="previewImage" alt="Responsive preview" />
          </div>
          <p class="viewport-meta" id="viewportMeta"></p>
        </div>

        <div class="info-grid" id="infoGrid"></div>

        <div class="note">The simulator renders the image inside a container scaled to the chosen viewport width, then reads the browser's actual <code>currentSrc</code> to report which candidate it selected — the same algorithm your visitors' browsers use, so this reflects real behavior rather than a guess.</div>
      </main>

      <p class="footer-note">Part of <a href="https://github.com/praveenscience/One-File-Tools">One File Tools</a>. Images load from their original URLs — nothing is uploaded or proxied.</p>
    </div>

    <script>
      /* ==========================================================
         Responsive Image Simulator
         Vanilla JS, no dependencies.
         ========================================================== */

      const srcsetInput = document.getElementById("srcsetInput");
      const sizesInput = document.getElementById("sizesInput");
      const fallbackInput = document.getElementById("fallbackInput");
      const srcsetError = document.getElementById("srcsetError");
      const breakpointTabs = document.getElementById("breakpointTabs");
      const viewportShell = document.getElementById("viewportShell");
      const previewImage = document.getElementById("previewImage");
      const viewportMeta = document.getElementById("viewportMeta");
      const infoGrid = document.getElementById("infoGrid");

      // Common device breakpoints to simulate. Width is the CSS viewport width
      // in pixels; the shell is scaled down visually via max-width for display,
      // but the actual <img> element is rendered at this width so srcset/sizes
      // resolve exactly as they would on a real device of that width.
      const BREAKPOINTS = [
        { id: "mobile-s", label: "Mobile S", width: 360 },
        { id: "mobile-l", label: "Mobile L", width: 480 },
        { id: "tablet", label: "Tablet", width: 768 },
        { id: "laptop", label: "Laptop", width: 1024 },
        { id: "desktop", label: "Desktop", width: 1440 },
        { id: "wide", label: "Wide", width: 1920 }
      ];

      let activeBreakpoint = BREAKPOINTS[2]; // Tablet by default.

      /** Renders the breakpoint tab buttons. */
      function renderTabs() {
        breakpointTabs.innerHTML = "";
        BREAKPOINTS.forEach((bp) => {
          const btn = document.createElement("button");
          btn.type = "button";
          btn.className = "bp-tab" + (bp.id === activeBreakpoint.id ? " active" : "");
          btn.textContent = bp.label + " · " + bp.width + "px";
          btn.addEventListener("click", () => {
            activeBreakpoint = bp;
            renderTabs();
            updatePreview();
          });
          breakpointTabs.appendChild(btn);
        });
      }

      /** Validates and normalizes the srcset textarea into a single-line attribute value. */
      function parseSrcset(rawText) {
        const lines = rawText
          .split(/[\n,]/)
          .map((line) => line.trim())
          .filter(Boolean);

        if (lines.length === 0) return { value: "", error: "Add at least one candidate (URL + width, e.g. image.jpg 800w)." };

        for (const line of lines) {
          if (!/^\S+\s+\d+w$/.test(line)) {
            return { value: "", error: 'Each candidate must be "URL widthw" (e.g. photo.jpg 800w). Problem: "' + line + '"' };
          }
        }

        return { value: lines.join(", "), error: null };
      }

      /** Formats dimensions as "W × H" or an em dash when unavailable. */
      function formatDimensions(width, height) {
        if (!width || !height) return "—";
        return width + " × " + height;
      }

      /** Renders the info cards describing the resolved image source. */
      function renderInfo() {
        infoGrid.innerHTML = "";
        const cards = [
          { label: "Viewport width", value: activeBreakpoint.width + "px" },
          { label: "Selected source", value: previewImage.currentSrc || "(loading…)" },
          { label: "Natural size", value: formatDimensions(previewImage.naturalWidth, previewImage.naturalHeight) },
          { label: "sizes value", value: sizesInput.value.trim() || "(none — defaults to 100vw)" }
        ];
        cards.forEach((card) => {
          const div = document.createElement("div");
          div.className = "info-card";
          const label = document.createElement("div");
          label.className = "label";
          label.textContent = card.label;
          const value = document.createElement("div");
          value.className = "value";
          value.textContent = card.value;
          div.appendChild(label);
          div.appendChild(value);
          infoGrid.appendChild(div);
        });
      }

      /**
       * Rebuilds the <img> with the current srcset/sizes/fallback and sizes the
       * viewport shell to the active breakpoint's width, then waits for the
       * browser to resolve currentSrc before updating the info cards.
       */
      function updatePreview() {
        const { value: srcsetValue, error } = parseSrcset(srcsetInput.value);
        srcsetError.textContent = error || "";
        if (error) return;

        viewportShell.style.width = activeBreakpoint.width + "px";
        viewportShell.style.maxWidth = "100%";

        previewImage.srcset = srcsetValue;
        previewImage.sizes = sizesInput.value.trim();
        previewImage.src = fallbackInput.value.trim();

        viewportMeta.textContent = "Rendered at " + activeBreakpoint.width + "px viewport width";

        // currentSrc is only reliably populated after the image finishes
        // resolving/loading, so refresh the info cards on load and also once
        // immediately for instant feedback while it loads.
        renderInfo();
        previewImage.onload = renderInfo;
      }

      [srcsetInput, sizesInput, fallbackInput].forEach((el) => {
        el.addEventListener("input", updatePreview);
      });

      renderTabs();
      updatePreview();
    </script>
  </body>
</html>