A curated collection of LGTM images for GitHub Pull Requests. High-performance image delivery with multiple formats, progressive loading, and infinite scroll pagination.

Live: lgtm.kkhys.me

LGTM generates and serves optimized review approval images with dynamic text overlay rendering. Built on Astro with server-side image processing, delivering AVIF/WebP/PNG formats with aggressive caching strategies.

LGTM Chrome Extension – One-click LGTM image insertion for GitHub code reviews.

Simply click the extension icon while browsing GitHub, and a random LGTM image is automatically copied to your clipboard as ready-to-paste HTML. The extension activates exclusively on GitHub domains with visual feedback (checkmark badge) and requires minimal permissions for privacy.

Key Features:

• One-click operation with GitHub-only activation
• Random image selection from the full gallery
• Instant clipboard copy with AVIF format
• Privacy-focused with minimal required permissions
• Lightweight design (< 50KB total)

Get it: Chrome Web Store | GitHub Repository

• Dynamic Image Generation – Server-rendered text overlays using Satori + Sharp
• Multi-Format Delivery – AVIF, WebP, PNG with automatic format negotiation
• Progressive Loading – Low-res WebP placeholder blur with smooth transitions
• Infinite Scroll – Paginated gallery with IntersectionObserver-based loading
• Responsive Images – Multiple size variants (400/1000/1200px) with 2x density support
• One-Click Markdown – Copy-to-clipboard with format selection (AVIF/WebP/PNG)
• SEO Optimized – Complete Open Graph, Twitter Card, JSON-LD, PWA manifest
• Edge Cached – Immutable responses with max-age 1 year

Core

• Astro 5.16 – Static site generation with Content Collections and pagination
• TypeScript 5.9 – Strictest compiler mode
• React 19 – Image generation components (JSX for Satori)

Image Processing

• Satori 0.18 – SVG/text rendering with custom fonts (BBHBartle-Regular)
• Sharp 0.34 – High-performance image manipulation (libvips)

Styling

• kiso.css 1.2 – Minimal CSS framework
• Custom design system with light/dark mode

Infrastructure

• Cloudflare Pages – Static hosting
• pnpm 10.26 – Workspace monorepo
• Biome 2.3 – Linting + formatting

Testing

• Vitest 4.0 – Unit testing framework
• Coverage: 100% statements, 88% branch, 100% functions

1. Load source image from lgtm-content submodule
2. Resize to target width (Sharp)
3. Render "LGTM" text as SVG (Satori, 2x resolution)
4. Composite text overlay with 85% opacity (blend mode: over)
5. Convert to AVIF/WebP/PNG
6. Serve with immutable cache headers

Implementation: src/components/lgtm-image.tsx

/                        → Gallery (paginated, 20 images per page)
/{page}                  → Gallery page N (infinite scroll target)
/{id}                    → Detail page with format selector
/{id}.{format}           → 800px image (default endpoint)
/{id}-{size}.{format}    → Custom size (400|1000|1200)
/api/og/default.png      → Default Open Graph image
/api/og/{id}.png         → Per-image Open Graph image
/api/favicon/*           → Dynamic favicon generation

Astro Content Collections with environment-based loader:

// src/content.config.ts
const lgtmBasePath = GITHUB_ACTIONS
  ? "./src/__fixtures__/lgtm-sample"
  : "./lgtm-content/lgtm";

const lgtm = defineCollection({
  loader: glob({ pattern: "**/index.md", base: lgtmBasePath }),
  schema: z.object({
    color: z.enum(["white", "black"]),  // Text color
    image: z.string(),                   // Source image filename
    isDraft: z.boolean().default(false), // Publishing control
  }),
});

Images stored in private Git submodule with ULID-based identifiers:

lgtm-content/lgtm/{ulid}/
  ├── index.md           # Frontmatter: color, image, isDraft
  └── {filename}.jpg     # Source image

• Gallery shows 20 images per page (IMAGES_PER_PAGE constant)
• Fisher-Yates shuffle on build for randomized display order
• IntersectionObserver triggers next page load 200px before scroll end
• Minimum 500ms loading indicator for better UX
• Non-first pages redirect to home if accessed directly

• Node.js 24.12 (via Volta)
• pnpm 10.26
• Bun (for utility scripts in lgtm-content/)

# Clone with submodules
git clone --recursive https://github.com/kkhys/lgtm.git

# Install dependencies
pnpm install

pnpm dev          # Start dev server (localhost:4321)
pnpm build        # Production build to ./dist
pnpm preview      # Preview production build
pnpm check        # Type checking (Astro + tsc)
pnpm lint         # Biome linting
pnpm lint:fix     # Auto-fix issues
pnpm test         # Run unit tests (Vitest)
pnpm coverage     # Test coverage report
pnpm all          # Full validation (build + check + lint:fix + test + coverage)

# Generate lowercase ULID for new images
cd lgtm-content
pnpm id

# Create timestamped memo
pnpm memo

# Create release tag (date-based versioning)
pnpm release [--dry-run]

1. Progressive Enhancement

   • 20x13px WebP placeholder with CSS blur filter (36px)
   • Full image fades in on load (300ms transition)
   • loading="eager" on detail page, lazy on gallery

2. Format Priorities (via <Picture> component)

   • AVIF: Best compression (~50% smaller than WebP)
   • WebP: Broad browser support
   • PNG: Lossless fallback

3. Build-Time Processing

   • Static generation of all image variants at build time
   • Pre-rendered text overlays with Satori
   • HTML/CSS/JS compression via @playform/compress

4. Runtime Caching

   • Cache-Control: public, max-age=31536000, immutable
   • Cloudflare CDN

5. Infinite Scroll

   • Fetch next page in background
   • Pre-connect and load images on demand
   • Smooth transition with loading states

Deployed locally via wrangler:

pnpm deploy   # Build and deploy to Cloudflare Pages

This runs pnpm build followed by wrangler pages deploy dist. The lgtm-content submodule must be available locally.

NODE_ENV              # development | production (auto-set)
GITHUB_ACTIONS        # CI detection (auto-set, switches to fixtures)

GitHub Actions uses fixture data (src/__fixtures__/lgtm-sample/) to avoid private submodule dependency in public CI.

lgtm/
├── src/
│   ├── assets/               # Static assets (fonts, images)
│   ├── components/
│   │   ├── icon/            # SVG icon components
│   │   ├── seo/             # SEO meta components
│   │   ├── lgtm-image.tsx   # Image generation logic
│   │   └── *.astro          # UI components
│   ├── config/              # Constants and configuration
│   ├── layouts/             # Page layouts
│   ├── pages/
│   │   ├── [...page].astro  # Paginated gallery
│   │   ├── [id].astro       # Detail page
│   │   ├── [id].[format].ts # Default image API
│   │   ├── [id]-[size].[format].ts # Sized image API
│   │   └── api/             # OG images and favicons
│   ├── styles/              # Global CSS
│   ├── content.config.ts    # Content Collections config
│   ├── __fixtures__/        # Test fixtures for CI
│   └── __tests__/           # Unit tests (Vitest)
│       ├── components/      # Component tests
│       ├── pages/           # API route tests
│       └── config/          # Configuration tests
├── lgtm-content/         # Git submodule (private)
├── scripts/                 # Build and release scripts
├── vitest.config.ts         # Vitest configuration
└── public/                  # Static public assets

Automated versioning with date-based tags:

pnpm release
# Creates tag: YYYY.MM.DD[-N]
# Generates GitHub release with changelog comparison

Process:

1. Generate version from current date
2. Check for existing tags, increment suffix if needed
3. Create and force-push Git tag
4. Generate GitHub Release via API
5. Return to original branch

MIT © Keisuke Hayashi

Built with precision. Served with speed.