Color-calculus NPM

color-calculus

A zero-dependency library of color conversion functions.

Supported Color Spaces

General Color Spaces
- lab (CIELAB with D65 Illuminant)
- hcl (lab in polar coordinates)
- xyz (CIEXYZ)
Commonly Used RGB Color Spaces
- sRGB
- AdobeRGB
- DisplayP3
- AppleRGB
CIECAM02 Perceptual Color Spaces
- JCh (CIECAM02 with D65 Illuminant)
- Jab (CIECAM02 with D65 Illuminant)

Usage

Install

npm install color-calculus

Example

Recommended method: import the library with ES module syntax. With this method, you can take advantage of the tree shaking features of a modern packaging tool such as rollup or webpack.

// Import the desired conversion function
import { xyz_to_lab } from "color-calculus";

// Convert xyz (10, 20, 30) to lab
const [l, a, b] = xyz_to_lab(10, 20, 30);

// Input can be supplied as an array
const lab = xyz_to_lab([10, 20, 30]);

Import with CommonJS syntax: useful when targeting Node.js:

// Import the desired conversion function
const { xyz_to_lab } = require("color-calculus");

Load via a script tag: useful when writing a simple HTML file:

<script
  src="node_modules/color-calculus/dist/color-calculus.umd.min.js"
  type="text/javascript"
></script>

<script type="text/javascript">
  const xyz_to_lab = ColorCalculus.xyz_to_lab;
</script>

The color-calculus.umd.min.js has zero dependency, you can copy the file from the node_modules folder to a different location and specify the src attribute accordingly.

Conversion Functions

All color conversions are named in the following convention:

/**
 * Convert from "source" colorspace to "destination" colorspace
 *
 * The parameter can be either three components, or an array of three components.
 * No default value is provided.
 */
source_to_destination(x1: number, x2: number, x3: number): [number, number, number ];
source_to_destination(x: [number, number, number]): [number, number, number];

source and destination can be any of the supported colorspaces, here is a list:

General Color Spaces
- lab (CIELAB with D65 Illuminant)
- hcl (Polar coordinates of lab)
- xyz (CIEXYZ)
Commonly Used RGB Color Spaces
- sRGB
- AdobeRGB
- DisplayP3
- AppleRGB
CIECAM02 Perceptual Color Spaces
- JCh (CIECAM02 with D65 Illuminant)

For example, to convert from sRGB to DisplayP3, you can use sRGB_to_DisplayP3.

Advanced CIECAM02 Functions

The CIECAM02 model captures color consistency. You can use this to convert colors between different viewing conditions.

import { CIECAM02 } from "color-calculus";

// TODO: Example

Derivatives of Conversion Functions

color-calculus allows you to compute the derivative (Jacobian) of some of the conversion functions. The derivatives would be useful if you want to do gradient-based optimizations for colors.

A gradient function follows the convention below:

/**
 * Convert from "source" colorspace to "destination" colorspace
 *
 * The parameter can be either three components, or an array of three components.
 * No default value is provided.
 */
source_to_destination_derivative(x1: number, x2: number, x3: number): [
  [number, number, number],
  [number, number, number],
  [number, number, number]
]
source_to_destination_derivative(x: [number, number, number]): [
  [number, number, number],
  [number, number, number],
  [number, number, number]
]

Color conversion functions are multivariate functions. The derivative of a multivariate function is called a Jacobian. color-calculus's derivative functions return Jacobian matrices in the following format:

For a color conversion that takes [x1, x2, x3] and outputs [y1, y2, y3],
the Jacobian is returned in this format:

[
  [ dy1/dx1, dy1/dx2, dy1/dx3 ],
  [ dy2/dx1, dy2/dx2, dy2/dx3 ],
  [ dy3/dx1, dy3/dx2, dy3/dx3 ]
]