Crate bevy_color

Representations of colors in various color spaces.

This crate provides a number of color representations, including:

• Srgba (standard RGBA, with gamma correction)
• LinearRgba (linear RGBA, without gamma correction)
• Hsla (hue, saturation, lightness, alpha)
• Hsva (hue, saturation, value, alpha)
• Hwba (hue, whiteness, blackness, alpha)
• Laba (lightness, a-axis, b-axis, alpha)
• Lcha (lightness, chroma, hue, alpha)
• Oklaba (lightness, a-axis, b-axis, alpha)
• Oklcha (lightness, chroma, hue, alpha)
• Xyza (x-axis, y-axis, z-axis, alpha)

Each of these color spaces is represented as a distinct Rust type.

Color Space Usage

Rendering engines typically use linear RGBA colors, which allow for physically accurate lighting calculations. However, linear RGBA colors are not perceptually uniform, because both human eyes and computer monitors have non-linear responses to light. “Standard” RGBA represents an industry-wide compromise designed to encode colors in a way that looks good to humans in as few bits as possible, but it is not suitable for lighting calculations.

Most image file formats and scene graph formats use standard RGBA, because graphic design tools are intended to be used by humans. However, 3D lighting calculations operate in linear RGBA, so it is important to convert standard colors to linear before sending them to the GPU. Most Bevy APIs will handle this conversion automatically, but if you are writing a custom shader, you will need to do this conversion yourself.

HSL and LCH are “cylindrical” color spaces, which means they represent colors as a combination of hue, saturation, and lightness (or chroma). These color spaces are useful for working with colors in an artistic way - for example, when creating gradients or color palettes. A gradient in HSL space from red to violet will produce a rainbow. The LCH color space is more perceptually accurate than HSL, but is less intuitive to work with.

HSV and HWB are very closely related to HSL in their derivation, having identical definitions for hue. Where HSL uses saturation and lightness, HSV uses a slightly modified definition of saturation, and an analog of lightness in the form of value. In contrast, HWB instead uses whiteness and blackness parameters, which can be used to lighten and darken a particular hue respectively.

Oklab and Oklch are perceptually uniform color spaces that are designed to be used for tasks such as image processing. They are not as widely used as the other color spaces, but are useful for tasks such as color correction and image analysis, where it is important to be able to do things like change color saturation without causing hue shifts.

XYZ is a foundational space commonly used in the definition of other more modern color spaces. The space is more formally known as CIE 1931, where the x and z axes represent a form of chromaticity, while y defines an illuminance level.

See also the Wikipedia article on color spaces.

Conversion

Conversion between the various color spaces is achieved using Rust’s native From trait. Because certain color spaces are defined by their transformation to and from another space, these From implementations reflect that set of definitions.

let color = Srgba::rgb(0.5, 0.5, 0.5);

// Using From explicitly
let linear_color = LinearRgba::from(color);

// Using Into
let linear_color: LinearRgba = color.into();

For example, the sRGB space is defined by its relationship with Linear RGB, and HWB by its with sRGB. As such, it is the responsibility of sRGB to provide From implementations for Linear RGB, and HWB for sRGB. To then provide conversion between Linear RGB and HWB directly, HWB is responsible for implementing these conversions, delegating to sRGB as an intermediatory. This ensures that all conversions take the shortest path between any two spaces, and limit the proliferation of domain specific knowledge for each color space to their respective definitions.

Other Utilities

The crate also provides a number of color operations, such as blending, color difference, and color range operations.

In addition, there is a Color enum that can represent any of the color types in this crate. This is useful when you need to store a color in a data structure that can’t be generic over the color type.

Color types that are either physically or perceptually linear also implement Add<Self>, Sub<Self>, Mul<f32> and Div<f32> allowing you to use them with splines.

Please note that most often adding or subtracting colors is not what you may want. Please have a look at other operations like blending, lightening or mixing colors using e.g. Mix or Luminance instead.

Example

use bevy_color::{Srgba, Hsla};

let srgba = Srgba::new(0.5, 0.2, 0.8, 1.0);
let hsla: Hsla = srgba.into();

println!("Srgba: {:?}", srgba);
println!("Hsla: {:?}", hsla);

Modules

• color_difference
  Module for calculating distance between two colors in the same color space.
• palettes
  Color palettes consisting of collections of const colors.
• prelude
  Commonly used color types and traits.

Structs

• Hsla
  Color in Hue-Saturation-Lightness (HSL) color space with alpha. Further information on this color model can be found on Wikipedia.
• Hsva
  Color in Hue-Saturation-Value (HSV) color space with alpha. Further information on this color model can be found on Wikipedia.
• Hwba
  Color in Hue-Whiteness-Blackness (HWB) color space with alpha. Further information on this color model can be found on Wikipedia.
• Laba
  Color in LAB color space, with alpha
• Lcha
  Color in LCH color space, with alpha
• LinearRgba
  Linear RGB color with alpha.
• Oklaba
  Color in Oklab color space, with alpha
• Oklcha
  Color in Oklch color space, with alpha
• Srgba
  Non-linear standard RGB with alpha.
• Xyza
  CIE 1931 color space, also known as XYZ, with an alpha channel.

Enums

• Color
  An enumerated type that can represent any of the color types in this crate.
• HexColorError
  Error returned if a hex string could not be parsed as a color.

Traits

• Alpha
  Methods for manipulating alpha values.
• ColorRange
  Represents a range of colors that can be linearly interpolated, defined by a start and end point which must be in the same color space. It works for any color type that implements Mix.
• ColorToComponents
  Trait with methods for converting colors to non-color types
• ColorToPacked
  Trait with methods for converting colors to packed non-color types
• Gray
  Trait for returning a grayscale color of a provided lightness.
• Hue
  Trait for manipulating the hue of a color.
• Luminance
  Methods for changing the luminance of a color. Note that these methods are not guaranteed to produce consistent results across color spaces, but will be within a given space.
• Mix
  Linear interpolation of two colors within a given color space.