Build a Dynamic OG Image Generator

// src/og/generator.ts — Dynamic OG image generation with HTML templates and caching
import puppeteer, { Browser } from "puppeteer";
import { Redis } from "ioredis";
import { createHash } from "node:crypto";

const redis = new Redis(process.env.REDIS_URL!);

let browser: Browser | null = null;

const OG_WIDTH = 1200;
const OG_HEIGHT = 630;

interface OGImageOptions {
  template: "article" | "product" | "profile" | "event";
  title: string;
  subtitle?: string;
  authorName?: string;
  authorAvatar?: string;
  category?: string;
  backgroundImage?: string;
  brandColor?: string;
  logo?: string;
  date?: string;
  price?: string;
  rating?: number;
}

// Generate OG image
export async function generateOGImage(options: OGImageOptions): Promise<Buffer> {
  // Check cache
  const cacheKey = `og:${createHash("md5").update(JSON.stringify(options)).digest("hex")}`;
  const cached = await redis.getBuffer(cacheKey);
  if (cached) return cached;

  // Get or create browser
  if (!browser) {
    browser = await puppeteer.launch({
      headless: true,
      args: ["--no-sandbox", "--disable-setuid-sandbox", "--disable-gpu"],
    });
  }

  const html = renderTemplate(options);
  const page = await browser.newPage();

  try {
    await page.setViewport({ width: OG_WIDTH, height: OG_HEIGHT });
    await page.setContent(html, { waitUntil: "networkidle0" });
    const imageBuffer = await page.screenshot({ type: "png" }) as Buffer;

    // Cache for 7 days
    await redis.setex(cacheKey, 86400 * 7, imageBuffer);

    return imageBuffer;
  } finally {
    await page.close();
  }
}

function renderTemplate(options: OGImageOptions): string {
  const brandColor = options.brandColor || "#6366f1";
  const logo = options.logo || "";

  switch (options.template) {
    case "article":
      return `<!DOCTYPE html>
<html>
<head><style>
  * { margin: 0; padding: 0; box-sizing: border-box; }
  body {
    width: ${OG_WIDTH}px; height: ${OG_HEIGHT}px;
    font-family: 'Inter', -apple-system, sans-serif;
    background: linear-gradient(135deg, #0f172a 0%, #1e293b 100%);
    display: flex; flex-direction: column; justify-content: space-between;
    padding: 60px 80px;
    color: white;
    overflow: hidden;
  }
  .top { display: flex; justify-content: space-between; align-items: center; }
  .category {
    background: ${brandColor}; color: white;
    padding: 8px 20px; border-radius: 20px;
    font-size: 18px; font-weight: 600; text-transform: uppercase;
    letter-spacing: 1px;
  }
  .logo { height: 40px; }
  .title {
    font-size: ${options.title.length > 60 ? "42px" : options.title.length > 40 ? "52px" : "60px"};
    font-weight: 800; line-height: 1.15;
    max-height: 280px; overflow: hidden;
    background: linear-gradient(90deg, #fff, #e2e8f0);
    -webkit-background-clip: text; -webkit-text-fill-color: transparent;
  }
  .bottom { display: flex; align-items: center; gap: 20px; }
  .avatar {
    width: 56px; height: 56px; border-radius: 50%;
    border: 3px solid ${brandColor}; object-fit: cover;
  }
  .author-info { display: flex; flex-direction: column; }
  .author-name { font-size: 20px; font-weight: 600; }
  .date { font-size: 16px; color: #94a3b8; }
  .accent-bar {
    position: absolute; bottom: 0; left: 0; right: 0;
    height: 6px; background: ${brandColor};
  }
</style></head>
<body>
  <div class="top">
    ${options.category ? `<span class="category">${escapeHtml(options.category)}</span>` : "<span></span>"}
    ${logo ? `<img class="logo" src="${logo}" />` : ""}
  </div>
  <div class="title">${escapeHtml(options.title)}</div>
  <div class="bottom">
    ${options.authorAvatar ? `<img class="avatar" src="${options.authorAvatar}" />` : ""}
    <div class="author-info">
      ${options.authorName ? `<span class="author-name">${escapeHtml(options.authorName)}</span>` : ""}
      ${options.date ? `<span class="date">${escapeHtml(options.date)}</span>` : ""}
    </div>
  </div>
  <div class="accent-bar"></div>
</body>
</html>`;

    case "product":
      return `<!DOCTYPE html>
<html>
<head><style>
  * { margin: 0; padding: 0; box-sizing: border-box; }
  body {
    width: ${OG_WIDTH}px; height: ${OG_HEIGHT}px;
    font-family: 'Inter', sans-serif;
    background: white;
    display: flex; overflow: hidden;
  }
  .left { flex: 1; padding: 60px; display: flex; flex-direction: column; justify-content: center; }
  .right { width: 400px; background: #f8fafc; display: flex; align-items: center; justify-content: center; }
  .right img { max-width: 300px; max-height: 400px; object-fit: contain; }
  .title { font-size: 44px; font-weight: 800; color: #0f172a; line-height: 1.2; margin-bottom: 20px; }
  .subtitle { font-size: 22px; color: #64748b; margin-bottom: 30px; }
  .price { font-size: 36px; font-weight: 700; color: ${brandColor}; }
  .rating { font-size: 24px; color: #f59e0b; margin-top: 10px; }
</style></head>
<body>
  <div class="left">
    <div class="title">${escapeHtml(options.title)}</div>
    ${options.subtitle ? `<div class="subtitle">${escapeHtml(options.subtitle)}</div>` : ""}
    ${options.price ? `<div class="price">${escapeHtml(options.price)}</div>` : ""}
    ${options.rating ? `<div class="rating">${"★".repeat(Math.round(options.rating))}${"☆".repeat(5 - Math.round(options.rating))}</div>` : ""}
  </div>
  <div class="right">
    ${options.backgroundImage ? `<img src="${options.backgroundImage}" />` : ""}
  </div>
</body>
</html>`;

    default:
      return `<html><body style="width:${OG_WIDTH}px;height:${OG_HEIGHT}px;display:flex;align-items:center;justify-content:center;font-family:sans-serif;background:#0f172a;color:white;font-size:48px;font-weight:bold;padding:60px;">${escapeHtml(options.title)}</body></html>`;
  }
}

function escapeHtml(str: string): string {
  return str.replace(/&/g, "&amp;").replace(/</g, "&lt;").replace(/>/g, "&gt;").replace(/"/g, "&quot;");
}

// HTTP endpoint
import { Hono } from "hono";
const app = new Hono();

app.get("/og/:template", async (c) => {
  const template = c.req.param("template") as OGImageOptions["template"];
  const title = c.req.query("title") || "Untitled";

  const image = await generateOGImage({
    template,
    title: decodeURIComponent(title),
    subtitle: c.req.query("subtitle"),
    authorName: c.req.query("author"),
    authorAvatar: c.req.query("avatar"),
    category: c.req.query("category"),
    brandColor: c.req.query("color"),
    date: c.req.query("date"),
    price: c.req.query("price"),
    rating: c.req.query("rating") ? parseFloat(c.req.query("rating")!) : undefined,
  });

  return c.body(image, {
    headers: {
      "Content-Type": "image/png",
      "Cache-Control": "public, max-age=604800",
    },
  });
});

export default app;