chart-image

Installation
SKILL.md

Chart Image Generator

Generate PNG chart images from data using Vega-Lite. Perfect for headless server environments.

Why This Skill?

Built for Fly.io / VPS / Docker deployments:

  • No native compilation - Uses Sharp with prebuilt binaries (unlike canvas which requires build tools)
  • No Puppeteer/browser - Pure Node.js, no Chrome download, no headless browser overhead
  • Lightweight - ~15MB total dependencies vs 400MB+ for Puppeteer-based solutions
  • Fast cold starts - No browser spinup delay, generates charts in <500ms
  • Works offline - No external API calls (unlike QuickChart.io)

Alternatives and why they don't work well on Fly:

  • canvas npm - Requires native compilation, fails on minimal Docker images
  • Puppeteer + Chart.js - 400MB+ Chrome download, slow cold starts, memory heavy
  • QuickChart API - External dependency, rate limits, privacy concerns
  • Plotly - Needs Puppeteer for static image export
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Installs
5
GitHub Stars
598
First Seen
Mar 23, 2026