Crate ansi_colours

ansi_colours converts between 24-bit sRGB colours and 8-bit colour palette used by ANSI terminals such as xterm on rxvt-unicode in 256-colour mode. The most common use case is when using 24-bit colours in a terminal emulator which only support 8-bit colour palette. It allows true-colours to be approximated by values supported by the terminal.

When mapping true-colour into available 256-colour palette, it tries to balance accuracy and performance. It doesn’t implement the fastest algorithm nor is it the most accurate, instead it uses a formula which should be fast enough and accurate enough for most use-cases.

Cargo features

To facilitate better interoperability the crate defines rgb crate feature (enabled by default). It adds support for the RGB type from rgb crate. Specifically, RGB8 (a.k.a. RGB<u8>) as well as RGB16 (a.k.a. RGB<u16>) types are supported.

Furthermore, ansi_term and termcolor features are available. They add support for Colour type from ansi_term crate and Color type from termcolor crate respectively. This includes support for calling ansi256_from_rgb with arguments of those types and implementation of ColourExt trait which extends the types with additional conversion methods.

Usage

Using this library with Cargo projects is as simple as adding a single dependency:

[dependencies]
ansi_colours = "1.1"

and then using one of the two functions that the library provides:

use ansi_colours::*;

fn main() {
    // Colour at given index:
    println!("{:-3}: {:?}", 50, rgb_from_ansi256(50));

    // Approximate true-colour by colour in the palette:
    let rgb = rgb::RGB8 { r: 100, g: 200, b: 150 };
    let index = ansi256_from_rgb(rgb);
    println!("{:?} ~ {:-3} {:?}", rgb, index, rgb_from_ansi256(index));
}

Traits

• AsRGB
  Type which represents a colour convertible to sRGB. Used to provide overloaded versions of ansi256_from_rgb function.
• ColourExt
  Extension to types representing ANSI colours adding methods converting between RGB and indexed (a.k.a. fixed) representations.

Functions

• ansi256_from_grey
  Returns index of a colour in 256-colour ANSI palette approximating given shade of grey.
• ansi256_from_rgb
  Returns index of a colour in 256-colour ANSI palette approximating given sRGB colour.
• rgb_from_ansi256
  Returns sRGB colour corresponding to the index in the 256-colour ANSI palette.