SKILL.md
OG image generation
Spec
- Dimensions: 1200×630 (OG 1.91:1) primary. Optional: 1080×1080 square (Instagram), 2:1 Twitter Card
summarylargeimage. - Format: PNG or JPEG, <5MB, served over absolute HTTPS URL, no auth headers.
- Text: Deterministic — use Satori + real fonts. Never sample typography from a diffusion model for OG cards; headlines get garbled (see logo skill § 3-word rule).
- Headline: ≤8 words, 64–96pt. Subheadline: ≤15 words, 28–36pt.
- Contrast: WCAG AA min 4.5:1 (Slack/Discord render inside their own color backgrounds).
Architecture
Default: template-based, no diffusion. The OG engine is:
- Satori — converts JSX or HTML+CSS to SVG with real font shaping.
@resvg/resvg-js— rasterizes the SVG to PNG deterministically, no system fonts leaked.- Optional hero layer — if brief says "with illustration," diffusion-generate a 1200×630 background and composite the Satori-rendered text layer on top.
@vercel/og— reference Satori wrapper if running inside Next.js/Vercel.
brief + brand bundle
↓
pick template (centered hero, left-aligned, minimal)
↓
fill template slots:
- title (required)
- subtitle (optional)
- logo.svg (optional, brand bundle)
- accent color (brand palette)
- background: solid | gradient | image
↓
[optional] generate background image (diffusion, see skills/hero or skills/illustration)
↓
satori(jsx) → SVG
↓
resvg.render(svg) → 1200×630 PNG
↓
validate: dimensions exact, <5MB, contrast, no-text-croppedTemplates (canonical)
| Template id | Layout | Use for |
|---|---|---|
centered_hero |
title + subtitle centered; logo bottom-left | launch posts, generic pages |
left_title |
title left-aligned; hero image right | feature pages, blog posts |
minimal |
title + brand color block | landing pages |
quote |
pull-quote + attribution | blog, documentation |
product_card |
logo + product name + tagline + accent bar | product pages |
Templates live as JSX/TSX strings in packages/mcp-server/src/templates/og/*.tsx.
Validation
- Width = 1200, height = 630 exactly.
- File <5MB.
- No text in outer 60px gutter (Slack/Twitter crop aggressively).
- WCAG AA contrast between headline and background (measure average luminance in the text-bbox region).
- If brand logo included: logo has a minimum size of 60×60px rendered.
Output
og/
├── og.png # 1200×630 PNG
├── og.jpg # 1200×630 JPEG (higher compression)
├── og-2x.png # 2400×1260 retina (optional)
└── meta.json