palette

A Rust library that makes linear color calculations and conversion easy and accessible for anyone. It provides both precision tools that lets you work in exactly the color space you want to, as well as a general color type that abstracts away some of the technical details.

Online documentation.

Linear?

Colors in, for example, images are often "gamma corrected" or stored in sRGB format as a compression method and to prevent banding. This is also a bit of a legacy from the ages of the CRT monitors, where the output from the electron guns was nonlinear. The problem is that these formats doesn't represent the actual intensities, and the compression has to be reverted to make sure that any operations on the colors are accurate. This library uses a completely linear work flow, and comes with the tools for transitioning between linear and non-linear RGB.

What Can It Do?

Palette provides tools for both color manipulation and conversion between color spaces. These are some highlights.

Color Spaces

RGB is probably the most widely known color space, but it's not the only one. You have probably used a color picker with a rainbow wheel and a brightness slider. That may have been an HSV or an HSL color picker, where the color is encoded as hue, saturation and brightness/lightness. There's also a group of color spaces that are designed to be perceptually uniform, meaning that the perceptual change is equal to the numerical change.

Selecting the proper color space can have a big impact on how the resulting image looks (as illustrated by some of the programs in examples), and Palette makes the conversion between them as easy as a call to from or into.

This example takes an sRGB color, converts it to CIE L*C*h°, shifts its hue by 180° and converts it back to RGB:

extern crate palette;
use palette::{Rgb, Lch, Hue};

let lch_color = Lch::from(Rgb::srgb(0.8, 0.2, 0.1));
let new_color: Rgb = lch_color.shift_hue(180.0.into()).into();

This results in the following two colors:

Hue Shift Comparison

Manipulation

Palette comes with a number of color manipulation tools, that are implemented as traits. These includes lighten/darken, saturate/desaturate and hue shift. These traits are only implemented on types where they are meaningful, which means that you can't shift the hue of an RGB color without converting it to a color space where it makes sense.

This may seem limiting, but the point is to avoid inconsistent behavior due to arbitrary defaults, such as saturating a gray color to red when there is no available hue information. The abstract Color type does still support every operation, for when this is less important.

The following example shows how the Color type is used to make a lighter and a desaturated version of the original.

extern crate palette;
use palette::{Color, Shade, Saturate};

let color = Color::srgb(0.8, 0.2, 0.1);
let lighter = color.lighten(0.1);
let desaturated = color.desaturate(0.5);

This results in the following three colors:

Manipulation Comparison

Gradients

There is also a linear gradient type which makes it easy to interpolate between a series of colors. This gradient can be used in any color space and it can be used to make color sequence iterators.

The following example shows two gradients between the same two endpoints, but one is in RGB and the other in is HSV space.

extern crate palette;
use palette::{Rgb, Hsv, Gradient};

let grad1 = Gradient::new(vec![
    Rgb::linear_rgb(1.0, 0.1, 0.1),
    Rgb::linear_rgb(0.1, 1.0, 1.0)
]);

let grad2 = Gradient::new(vec![
    Hsv::from(Rgb::linear_rgb(1.0, 0.1, 0.1)),
    Hsv::from(Rgb::linear_rgb(0.1, 1.0, 1.0))
]);

The RGB gradient goes through gray, while the HSV gradients changes only the hue:

Gradient Comparison

What It Isn't

This library is only meant for color manipulation and conversion. It's not...

...an image manipulation library. It will only handle colors, and not whole images.
...an optimal pixel format. The colors are represented by linear 32-bit floats with a mandatory alpha component. It's not a compact format.

You will have to look elsewhere for those features.

Contributing

All sorts of contributions are welcome, no matter how huge or tiny, so take a look at CONTRIBUTING.md for guidelines, if you are interested.

License

Licensed under either of

Apache License, Version 2.0, (LICENSE-APACHE or http://www.apache.org/licenses/LICENSE-2.0)
MIT license (LICENSE-MIT or http://opensource.org/licenses/MIT)

at your option.

Contribution

Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in the work by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.

palette 0.1.0