# OpenColor

> OpenColor is a free browser app and open API that matches a measured color
> (CIELAB) to named color standards — RAL, Pantone, NCS, Munsell, and paint
> fandecks (Sherwin-Williams, Benjamin Moore). It reads a Datacolor ColorReader
> (CR100) colorimeter directly over Web Bluetooth, and also works as a standalone
> color-lookup API that anyone (or any agent) can query with L*a*b* values.

## What it does

- Reads CIELAB (L*, a*, b*) from a Datacolor ColorReader over Web Bluetooth in
  Chrome/Edge (desktop or Android). The same CR100 hardware is white-labeled by
  paint brands (PPG, Benjamin Moore, RAL, Dunn-Edwards, Caparol, Tikkurila,
  Dulux, Sherwin-Williams, Lechler); those should work too, though only the
  Datacolor unit is verified.
- Finds the nearest named colors across ~11,400 references in 8 systems, ranked
  by CIEDE2000 color difference.

## API (no key, CORS-open)

Match a CIELAB color to the nearest standards:

`GET https://opencolor.app/api/match?L=<0-100>&a=<number>&b=<number>`

Optional query params:
- `mode=per-system` (default; best match in each system, ranked) or `mode=pooled`
  (top-N nearest overall)
- `limit=<1-50>`
- `system=<id>` to restrict to one system (ids in /data/index.json)

Examples:
- https://opencolor.app/api/match?L=53.24&a=80.09&b=67.20
- https://opencolor.app/api/match?L=93.9&a=0.1&b=1.7&mode=pooled&limit=5
- https://opencolor.app/api/match?L=45&a=60&b=35&system=ral_classic&limit=10

OpenAPI spec: https://opencolor.app/openapi.json — full reference:
https://opencolor.app/llms-full.txt

Each match returns: `system`, `systemId`, `code`, `name`, `hex`, `L`, `a`, `b`,
and `deltaE` (CIEDE2000).

## Datasets (CIELAB, D65/2° observer)

- All colors in one file: https://opencolor.app/data/all.json
- Index of systems + per-system files: https://opencolor.app/data/index.json
- Per-system: https://opencolor.app/data/<systemId>.json

Systems: CSS named colors, RAL Classic, Pantone PMS Coated (C), Pantone PMS
Uncoated (U), NCS (Natural Color System), Munsell, Sherwin-Williams, Benjamin
Moore. Some CIELAB values are published by the source; others are derived from
published sRGB hex (each entry has a `method` field).

## Notes

- The app runs entirely client-side; scans and history stay in the browser.
- On-screen swatches are approximations (sRGB gamut); the numeric CIELAB and
  CIEDE2000 values are authoritative.