Chroma - Everything you want to do with colors.

nimble install chroma

API reference

This library has no dependencies other than the Nim standard libarary.

About

This library works with colors and color spaces. Easly parse and transform colors. Many different color spaces. Optimized, fast and consistant.

Parse/Format

Common color parsers and formatters:

• hex - FFFFFF
• HtmlHexTiny - #FFF
• HtmlHex - #FFFFFF
• HtmlRgb - rgb(255, 255, 255)
• HtmlRgba - rgba(255, 255, 255, 1.0)
• HtmlName - white
• HexAlpha - FFFFFFFF
• parseHtmlColor - Any of the HTML formats.

Color Spaces

Conversion from and to these colors spaces:

• 8-bit RGB
• 8-bit RGBA
• CMY colors are reverse of rgb
• CMYK colors are used in printing
• HSL attempts to resemble more perceptual color models
• HSV models the way paints of different colors mix together
• YUV origially a television color format, still used in digital movies
• XYZ (CIE XYZ; CIE 1931 color space)
• LAB (CIE L*a*b*, CIELAB), derived from XYZ (Note: a fixed white point is assumed)
• CIELCh, LAB in polar coordinates (type: ColorPolarLAB)
• LUV (CIE L*u*v*, CIELUV), derived from XYZ (Note: a fixed white point is assumed)
• CIELCH, LUV in polar coordinates (type: ColorPolarLUV), often called HCL
• Oklab (https://bottosson.github.io/posts/oklab/)

The default type is an RGB based type using float32 as its base type (with values ranging from 0 to 1) and is called Color. All the above color spaces have corresponding type names of Color<ColorSpaceName>, where ColorSpaceName is the name in the bullet points above (unless specified by "type:" in parenthesis).

Convenience procs to convert from and to the default type Color are provided in the form of

• proc color(c: Color<ColorSpaceName>): Color

and the inverse:

• proc <colorSpaceName>(c: Color): Color<ColorSpaceName>.

and using the field names:

• proc <colorSpaceName>(<fieldName1>, <fieldName2>, <fieldName3>: <fieldType>): Color<ColorSpaceName>

Color Functions

You can use these to change colors you already have

• lighten(color, amout) Lightens the color by amount 0-1
• darken(color, amout) Darkens the color by amount 0-1
• saturate(color, amout) Saturates (makes brighter) the color by amount 0-1
• desaturate(color, amout) Desaturate (makes grayer) the color by amount 0-1
• spin(color, degrees) Rotates the hue of the color by degrees (0-360)
• mix(colorA, colorB) Mixes two colors together using CMYK

A distance function is provided that implements CIEDE2000 color difference formula

• distance(colorA, colorB) Distance between two colors

This distance is designed to be perceptually uniform and it can be used to answer the question: "What is a set of colors that are imperceptibly/acceptably close to a given reference?". A value of 5.0 is used as reference in github linguist library: any color with distance less than 5.0 from one of the existing colors is not allowed.

Example

import chroma

let
    a = color(0.7,0.8,0.9)
    b = color(0.2,0.3,0.4,0.5)

echo a.toHex()
echo parseHex("BADA55")
echo parseHtmlName("red")
echo hsv(b).color()
echo a.darken(0.2)
echo mix(a, b)