Crate farg 

A Rust library for colorimetry, color space conversions, and color manipulation.

Farg provides context-aware color conversions with f64 precision, spectral data processing, and chromatic adaptation. It’s designed to serve web developers with sensible defaults while giving colorimetrists full control over illuminants, observers, and adaptation transforms.

Quick Start

Create colors, convert between spaces, and manipulate components:

use farg::space::{ColorSpace, Rgb, Srgb, Xyz};

// Create an sRGB color from 8-bit values
let color = Rgb::<Srgb>::new(255, 87, 51);

// Convert to CIE XYZ
let xyz: Xyz = color.to_xyz();
let [x, y, z] = xyz.components();

// Adjust luminance while preserving chromaticity
let brighter = xyz.with_luminance_scaled_by(1.2);

Architecture

Colors in farg exist within a viewing context consisting of:

• An Illuminant — the light source (e.g., D65 daylight, D50 for print)
• An Observer — the human visual system model (e.g., CIE 1931 2°)
• A ChromaticAdaptationTransform — how the eye adjusts to different lighting

By default, colors use the D65 illuminant with the CIE 1931 2° observer and the Bradford chromatic adaptation transform. This matches the standard sRGB viewing environment.

Conversions flow through hub color spaces to minimize implementation complexity:

• Xyz — universal hub for device-independent spaces
• Lms — cone response space used for chromatic adaptation
• Linear RGB — intermediate hub for the RGB family (gamma decode → linear → XYZ)

Color Spaces

The space module contains all color space types and the ColorSpace trait. Xyz, Lms, and Srgb are always available. Additional RGB spaces are enabled through feature flags:

[dependencies]
farg = { version = "0.1", features = ["rgb-display-p3", "rgb-adobe-rgb"] }

All color spaces implement the ColorSpace trait, providing a common interface for conversions, luminance operations, and component access.

Chromatic Adaptation

Adapt colors between different illuminants using a ChromaticAdaptationTransform:

use farg::{Cat, ColorimetricContext, Illuminant};
use farg::space::Xyz;

let d50_context = ColorimetricContext::new()
    .with_illuminant(Illuminant::D50)
    .with_cat(Cat::BRADFORD);

let color = Xyz::new(0.95047, 1.0, 1.08883);
let adapted = color.adapt_to(d50_context);

Spectral Data

Farg includes spectral power distribution (SPD) data for all standard illuminants and color matching function (CMF) data for all standard observers. Access spectral data through the SpectralTable trait:

use farg::{Illuminant, Observer, SpectralTable};

let d65 = Illuminant::D65;
let spd = d65.spd();
let power_at_550nm = spd.at(550);

let observer = Observer::CIE_1931_2D;
let cmf = observer.cmf();
let xyz = cmf.spectral_power_distribution_to_xyz(&spd);

Chromaticity

The chromaticity module provides coordinate systems for representing color independent of luminance. Xy (CIE 1931) is always available; additional systems like Uv and Upvp are feature-gated.

Feature Flags

Farg uses granular feature flags so you only compile what you need. The default feature enables cat-bradford. The D65 illuminant, CIE 1931 2° observer, sRGB, and XYZ/LMS spaces are always available regardless of feature selection.

Feature	Contents
full	Everything
all-cats	All chromatic adaptation transforms
all-chromaticity	All chromaticity coordinate systems
all-illuminants	All standard illuminants
all-observers	All standard observers
all-rgb-spaces	All RGB color spaces

Modules

chromaticity

contrast

correlated_color_temperature

Correlated Color Temperature (CCT) estimation.

distance

space

Structs

ChromaticAdaptationTransform

A 3x3 matrix transform for adapting colors between different illuminant white points.

ChromaticityCoordinates

Spectral locus chromaticity coordinates derived from color matching functions.

ColorMatchingFunction

CIE color matching functions mapping wavelengths to XYZ tristimulus responses.

ColorimetricContext

Defines the viewing conditions for colorimetric calculations.

ConeFundamentals

Spectral cone sensitivity functions mapping wavelengths to LMS cone responses.

ConeResponse

An LMS cone response at a single wavelength.

FairchildModifier

Modifier for deriving new Observer instances from existing ones.

Illuminant

A standard or custom illuminant (light source) defined by its spectral power distribution.

IlluminantBuilder

Builder for constructing custom Illuminant instances.

Observer

A standard or custom observer defined by color matching functions.

ObserverBuilder

Builder for constructing custom Observer instances.

SpectralPowerDistribution

Spectral power distribution — the power of a light source at each wavelength.

TristimulusResponse

An XYZ tristimulus response at a single wavelength.

Enums

Error

Errors that can occur during color operations.

IlluminantType

The category of an illuminant.

Traits

SpectralTable

Common interface for wavelength-indexed spectral data.

Type Aliases

Cat

Shorthand alias for ChromaticAdaptationTransform.

Cmf

Shorthand alias for ColorMatchingFunction.

Spd

Shorthand alias for SpectralPowerDistribution.