Iridescence

Sophisticated representation of color

About

Iridescence implements several algorithms for working with colors represented in different forms.

Features

Availability

Iridescence is available as a binary for Scala 3.4.0 and later, from Maven Central. To include it in an sbt build, use the coordinates:

libraryDependencies += "dev.soundness" % "iridescence-core" % "0.1.0"

Getting Started

Iridescence provides seven different ways of representing colors:

Each color model uses either three or four continuous coordinates, all represented in Iridescence as Doubles in the unit interval (0 ≤ *c* ≤ 1), to describe an apparently full spectrum of colors perceived by the human eye.

Given the complex nature of sight and color, different models make different tradeoffs in their representations of different colors. While sRGB is the most direct representation of the colored light emitted by a computer monitor, and indeed the most common representation for computers, CMY and CMYK are more common in printing.

Meanwhile, the HSL and HSV representations representations use the natural qualititative properties of hue, saturation, lightness and brightness, and the XYZ and CIELAB color spaces are derived empirically. CIELAB attempts to maintain the property that the Euclidean distance between two colors is proportional to the perceptual difference between those colors, as determined by experimentation.

The particular color model should be chosen according to the requirements of the particular task.

A Quick Example

import soundness.*

given profile = profiles.Ultralume50

val pink: Cielab = colors.Ivory.cielab.mix(colors.DarkMagenta.cielab)
val palePink: Srgb = pink.srgb.hsv.tint(0.5).srgb
println(s"${color.ansiFg24}Hello World!")

Types

Iridescence provides case classes to immutably represent each of the seven color models, above. Colors in one representation can be directly converted into many of the other representations, and the remaining conversions can be performed indirectly.

In general, every color representation provides the Color#srgb method to convert it to an Srgb value. Conversely, the Srgb type provides the methods cmy, cmyk, cielab, xyz, hsv and hsl to convert to these alternative representations.

While it would be possible to provide an n×n set of methods for converting between any pair of representations, conversions which rely on an unspecified intermediate representation (for example converting between HSL and CMYK) are generally not provided unless the intermediate representation is a necessary step in the calculation. This is to make it clear when conversions are happening.

For example, the methods Hsl#srgb and Srgb#xyz both exist, but Hsl#xyz is not implemented. However, Srgb#cielab is provided, even though the conversion is made via an intermediate XYZ value.

Here are some examples:

val DeepPink: Srgb = Srgb(1, 0.078, 0.576)
val Gold: Hsv = Srgb(1, 0.843, 0).hsv
val Gold2: Cmyk = Gold.srgb.cmyk

Palettes

The webColors object provides a standard palette of about 140 named colors defined in sRGB space.

Color profiles

Certain color representations rely on additional information that characterizes the conditions under which the colors are encoded, and this information is necessary for conversions between certain color spaces.

For example, to convert from Srgb to Cielab requires a profile. Profiles are provided through the Profile type, and several are provided in the profiles object. These should be specified, implicitly or explicitly with each conversion, like so:

val color = DeepPink.cielab(using profiles.MidMorningDaylight)

or,

given Profile = profiles.CoolFluorescent
val color = LawnGreen.xyz

For generality, conversions to Srgb always require a profile to be given (even for conversions where it is not used). This restriction may be lifted later. A good default profile to use is the Daylight profile.

given Profile = profiles.Daylight

Color methods

Additional methods are provided on certain color types for producing new colors from old. In general, these methods are particular to the color model being used.

For example, the methods saturate, desaturate, pure and rotate (for changing the hue) are provided on Hsl and Hsv types, while Hsv additionally provides shade, tint and tone methods. These latter methods take black and/or white parameters to specify the amount of shading, tinting or toning to be applied.

Cielab provides a delta method for comparing two colors (returning a Double in the unit interval), and the mix method for combining two colors. Cielab#mix takes another Cielab color as its first parameter, and a mix ratio (again, in the unit interval) as an optional second parameter. If left unspecified, it defaults to the midpoint between the two colors.

Use of these methods might typically involve converting a color to the model which defines them, then applying them as necessary, before converting back. For example,

webColors.IndianRed.hsv.tone(0.2, 0.4).srgb

Serialization

Different formats, languages and protocols will represent colors as strings in a number of different ways. Iridescence provides serialization methods to the following formats:

These are available on the Srgb type, with the exception of Hsl#css.

Limitations

There is no support for transparency.

License

Iridescence is copyright © 2024 Jon Pretty & Propensive OÜ, and is made available under the Apache 2.0 License.