hoelee-blog/scripts/og-gen

og-gen — per-post OG image generator

Generates a branded 1200×630 social-share image for a blog post, matching the site's cobalt-blue #295cff branding, the logo-square.png mark, and the "terminal / debugging" visual style.

Usage

node scripts/og-gen/generate.mjs <post-slug>

Reads frontmatter (title, category, tags) from src/content/posts/<slug>.md, fills template.html, renders with headless Chrome, and writes public/og/<slug>.png.

The post's frontmatter needs ogImage: /og/<slug>.png so the blog serves it (layout already renders og:image + width/height; PostList shows it as a card thumbnail).

Customizing the terminal box

Each post shows a "terminal" panel (the red error / green fix lines). Add an entry keyed by slug in TERMINALS inside generate.mjs, using these tokens:

<div class="line"><span class="prompt">$</span><span class="cmd">command</span></div>
<div class="line"><span class="prompt">&nbsp;</span><span class="err">error line</span></div>
<div class="line"><span class="prompt">$</span><span class="cmd">fix</span><span class="fix">→ done ✓</span></div>

No entry → a generic default terminal.

Requirements

• Google Chrome at C:\Program Files\Google\Chrome\Application\chrome.exe (override with CHROME_PATH env var).
• Node 20+.

Notes

• PNG (not JPG) is intentional: for flat UI/terminal art, PNG is smaller and sharper than JPG (see commit history).
• The logo-square.png referenced lives at public/logo-square.png.

---

v2 pipeline ("one art, four targets") — render_from_art.mjs

The consultant-approved redesign replaces the generated terminal panels with one zero-text base-art frame per post, composited into four assets:

Target	Path	Size
hero banner	public/banners/<slug>.webp (+ .jpg fallback from frontmatter)	1600×900
social card	public/og/<slug>.jpg (EN), public/og/zh-<slug>.jpg (ZH)	1200×630
bento/list thumb	public/og/thumb/<slug>-800.webp	800×420
small thumb	public/og/thumb/<slug>-400.webp	400×210

The card is template-v2.2.html (frosted bento + blueprint grid + full-width evidence bar) filled from the post's own frontmatter plus art-meta.json; the self-fitting headline script reports FIT <n>px through <title>, and a render that does not settle fails instead of shipping a silently-shrunken card.

# metadata first: art path (default <art-dir>/<slug>.png) + a HAND-WRITTEN evidence line
$EDITOR scripts/og-gen/art-meta.json

node scripts/og-gen/render_from_art.mjs --only <slug>[,<slug>] --out /tmp/og-check
node scripts/og-gen/render_from_art.mjs --all            # writes into public/

• --format jpg (default) or png. JPEG is the default because it is measured: a composited card renders 558 KB as PNG and lands at 84 KB at mozjpeg q85 (256-colour PNG = 240 KB). The default site card already ships as JPG for the same reason.
• evidence is required and never derived — it is editorial text, and inventing one from the description is the "invented specificity" failure the blog avoids. A missing entry aborts with the slug list.
• ogTitle_en / ogTitle_zh shorten only the card's headline (the article keeps its real title) — the consultant's answer to the English headline-rag problem.
• Reproducibility check: re-rendering the two sample posts produced banners and 800px thumbs byte-identical to the consultant's accepted delivery (sha256 16e6a7b0…, f3b29f38…, c4e28291…, 8095ec6c…).
• ⚠ Changing ogImage from .png to .jpg also needs PostList.astro's thumb helper updated (/\.(png|jpe?g)$/), or the listing derives …-800.webp from slug.jpg and every thumb 404s.