Setup & Installation
Or with the ClawHub CLI, for registry-managed skill folders outside a full OpenClaw workspace:
Version History
chart-image v2.5.1 - Version bump from 2.4.0 to 2.5.1. - Documentation updated (README.md, SKILL.md): no new features or options documented. - No changes to code structure or CLI arguments are documented.
What This Skill Does
Generates PNG or SVG chart images from JSON data using Vega-Lite. Supports line, bar, area, pie, donut, candlestick, heatmap, multi-series, and stacked charts. Runs as a pure Node.js script with no browser or native compilation required.
Unlike Puppeteer-based chart tools, it uses prebuilt Sharp binaries and generates charts in under 500ms with no browser overhead, making it suitable for Fly.io, Docker, and VPS deployments.
When to use it
- Embedding price charts in trading alerts
- Visualizing server metrics in monitoring reports
- Generating activity heatmaps from log data
- Plotting time series for scheduled digest emails
- Creating candlestick charts for financial dashboards
Example Workflow
Here's how your AI assistant might use this skill in practice.
User asks: Plot hourly temperature readings from today as a dark-mode line chart with change annotation
- 1Format temperature data as a JSON array with x (time) and y (temperature) fields
- 2Run chart.mjs with --type line, --x-type temporal, --dark, --show-change, --show-values flags
- 3Set --title and --output path under /data/clawd/tmp/
- 4Send the generated PNG to the user's channel using the message tool with filePath
A dark-mode line chart PNG showing temperature over time with a +/-% change label at the last data point