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Saihex Studios' HTML2WebP V1.2

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HTML2WebP is a lightweight* Deno server that converts HTML into WebP images, supporting dynamic placeholders for template values.

It’s designed for stability and automation: the server automatically exits every 48 hours, relying on Docker’s restart policy (on-failure) to keep instances fresh.

Disclaimer*: The app itself might be light. But, Chromium, one of its dependencies is not.

⚠️ SECURITY WARNING

Astral is configured to run Chromium without its internal sandbox inside the Docker container.
This is safe as long as the container itself is properly isolated.

• Do NOT run the container with --network=host.
• Do NOT expose your API port to the host machine during local testing.
• In production, always run behind a reverse proxy (e.g., Nginx, Caddy) and expose only the necessary ports.

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Features

• Dynamic HTML > WebP rendering
• Template placeholders using {{key}} syntax
• Fresh page per request to avoid contamination
• Page pooling with up to 5 concurrent requests to prevent server overload
• Default resolution: 1700x893 (used if unspecified or invalid)
• Health check endpoint: /health
• Port: 8080
• Internal in-memory result caching with custom identifier

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Request Structure

Send JSON to the server:

{
  "html": "string",
  "cache_id": "saihex_public_blog_post_12345",
  "width": 1700,
  "height": 780,
  "values": {
    "title": "My Blog Post",
    "uploader_username": "Isky",
    "status": "Edited",
    "date": "2025-08-19",
    "id": "12345",
    "uploader_pfp": "https://example.com/avatar.png"
  },
  "image_values": [
    "uploader_pfp"
  ]
}

• html
  The raw HTML template that will be rendered. Placeholders inside this template are substituted using values from values.

• width / height
  Dimensions of the rendered output. Optional; defaults to 1700 × 780 if not provided.

• values
  A map of placeholder keys → string values. These are substituted into the HTML during rendering.

  • Some values may be plain text (like title, date).
  • Others may be image URLs (like uploader_pfp).

• cache_id
  Identifier used for caching (Optional).

  • If the string is empty or invalid, no cache entry will be created.
  • If valid, the rendered result is cached for 1200 seconds (20 minutes).
  • The cache duration is fixed and cannot be changed at runtime.

• image_values
  An array of keys from values that represent image URLs which should be fetched and embedded as base64 blobs before rendering.

  • Ensures rendering doesn’t depend on external services.
  • Particularly important for services like Gravatar, which may cause incomplete image otherwise.

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Example Use Case

• OG Image Generator for blog posts, websites, or social media
• Can dynamically render different posts using the same template