color_models #

A package with models for defining colors in the CMYK, HSI, HSL, HSP, HSB, LAB, Oklab, RGB, and XYZ color spaces, with methods for converting colors between spaces and adjusting their properties.

For use with Flutter, see: https://pub-web.flutter-io.cn/packages/flutter_color_models

Check out palette, a package for creating, generating, and modifying color palettes.

Usage #

import 'package:color_models/color_models.dart';

Color Spaces #

color_models exposes models for the CMYK, HSI, HSL, HSP, HSB, LAB, RGB, and XYZ color spaces; represented as [CmykColor], [HsiColor], [HslColor], [HspColor], [HsbColor], [LabColor], [OklabColor] [RgbColor], and [XyzColor] respectively.

Creating Colors #

Colors can be created by constructing a [ColorModel] directly, or with the [fromList] or [extrapolate] constructors. [extrapolate] accepts each model's respective values on a 0 to 1 scale, and extrapolates them to their normal scale.

Each model posesses values for each property of their respective acronyms, as well as an optional [alpha] value.

// Each of the below colors is red at 100% opacity.

// RGB without alpha
RgbColor(255, 0, 0);
RgbColor.fromList(<num>[255, 0, 0]);
RgbColor.extrapolate(<num>[1.0, 0.0, 0.0]);

// RGB with alpha
RgbColor(255, 0, 0, 1.0);
RgbColor.fromList(<num>[255, 0, 0, 255]);
RgbColor.extrapolate(<num>[1.0, 0.0, 0.0, 255]);

// CMYK without alpha
CmykColor(0.0, 100.0, 100.0, 0.0);
CmykColor.fromList(<num>[0.0, 100.0, 100.0, 0.0]);
CmykColor.extrapolate(<num>[0.0, 1.0, 1.0, 0.0]);

// CMYK with alpha
CmykColor(0.0, 100.0, 100.0, 0.0, 1.0);
CmykColor.fromList(<num>[0.0, 100.0, 100.0, 0.0, 255]);
CmykColor.extrapolate(<num>[0.0, 1.0, 1.0, 0.0, 255]);

// HSL without alpha
HslColor(0.0, 100.0, 50.0);
HslColor.fromList(<num>[0.0, 100.0, 50.0]);
HslColor.extrapolate(<num>[0.0, 1.0, 0.5]);

// HSL with alpha
HslColor(0.0, 100.0, 50.0, 1.0);
HslColor.fromList(<num>[0.0, 100.0, 50.0, 255]);
HslColor.extrapolate(<num>[0.0, 1.0, 0.5, 255]);

Converting Colors Between Spaces #

Each color model has methods to convert itself to every other color model.

CmykColor toCmykColor();

HsiColor toHsiColor();

HslColor toHslColor();

HspColor toHspColor();

HsbColor toHsbColor();

LabColor toLabColor();

OklabColor toOklabColor();

RgbColor toRgbColor();

XyzColor toXyzColor();

Altenatively, each color model has a constructor [ColorModel.from] that returns a color from any color space in the color space being called.

// Create a HSB color
var originalColor = HsbColor(0.3, 0.8, 0.7);

// Convert it to RGB => RgbColor(64, 179, 36)
var rgbColor = RgbColor.from(originalColor);

// Then to CMYK => CmykColor(64.25, 0, 79.89, 29.8)
var cmykColor = CmykColor.from(rgbColor);

// Back to HSB => HsbColor(0.3, 0.8, 0.7)
var hsbColor = HsbColor.from(cmykColor);

Note: All color conversions use the RGB color space as an intermediary. To minimize the loss of precision when converting between other color spaces, [RgbColor] privately stores the RGB values as [num]s rather than [int]s. The [num] values can be returned as a list with [RgbColor]'s toPreciseList() method.

Color Adjustments #

For convenience, each [ColorModel] has 2 getters, [inverted] and [opposite], and 3 methods, [cooler], [warmer] and [rotateHue], for generating new colors.

[inverted] inverts the colors properties within their respective ranges, excluding hue, which is instead rotated 180 degrees.

final orange = RgbColor(255, 144, 0);

print(orange.inverted); // RgbColor(0, 111, 255);

[opposite] returns the color with the hue opposite this. [opposite] is shorthand for color.rotateHue(180).

[rotateHue] rotates the hue of the color by the [amount] specified in degrees. Colors in the CMYK, LAB, RGB, and XYZ color spaces will be converted to and from the HSL color space where the hue will be rotated.

final orange = RgbColor(255, 144, 0);

print(orange.opposite); // RgbColor(0, 111, 255);

print(orange.rotateHue(30)); // RgbColor(239, 255, 0);

print(orange.rotateHue(-30)); // RgbColor(255, 17, 0);

[warmer] and [cooler] will rotate the hue of the color by the [amount] specified towards 90 degrees and 270 degrees, respectively. The hue's value will be capped at 90 or 270.

final orange = RgbColor(255, 144, 0);

print(orange.warmer(30)); // RgbColor(239, 255, 0);

print(orange.cooler(30)); // RgbColor(255, 17, 0);

Interpolating Between Colors #

Each color model has a method, [lerpTo], that calculates a specified number of steps between this color and a color provided to the method, returning all of the colors inbetween the two colors in a list. Colors will be returned in the color space of the color the method is called on.

final color1 = RgbColor(255, 0, 0); // red
final color2 = RgbColor(0, 0, 255); // blue

/// Calculate a [List<RgbColor>] of 5 colors: [color1], [color2] and the 3 steps inbetween.
final colors = color1.lerpTo(color2, 3);

// [RgbColor(255, 0, 0, 255), RgbColor(191, 0, 64, 255), RgbColor(128, 0, 128, 255), RgbColor(64, 0, 191, 255), RgbColor(0, 0, 255, 255)]
print(colors);

/// To return only the steps in between [color1] and [color2], the [excludeOriginalColors] parameter can be set to `true`.
final steps = color1.lerpTo(color2, 3, excludeOriginalColors: true);

// [RgbColor(191, 0, 64, 255), RgbColor(128, 0, 128, 255), RgbColor(64, 0, 191, 255)]
print(steps);

Augmenting Palettes #

color_models provides an extension on Iterable<ColorModel> for augmenting color palettes. It works by distributing the colors in the iterable across an abstract gradient and calculating new colors based on their positions within the gradient.

final palette = <ColorModel>[
  RgbColor(255, 0, 0),
  RgbColor(0, 255, 0),
  RgbColor(0, 0, 255),
];

// [RgbColor(255, 0, 0), RgbColor(128, 128, 0), RgbColor(0, 255, 0), RgbColor(0, 128, 128), RgbColor(0, 0, 255)]
final newPalette = palette.augment(5);

[stops] can be provided to map the colors in the list to positions within the abstract gradient.

final palette = <ColorModel>[
  RgbColor(255, 0, 0),
  RgbColor(0, 255, 0),
  RgbColor(0, 0, 255),
];

// [RgbColor(255, 0, 0), RgbColor(170, 85, 0), RgbColor(85, 170, 0), RgbColor(0, 255, 0), RgbColor(0, 0, 255)]
final newPalette = palette.augment(5, stops: [0.0, 0.75, 1.0]);

[colorSpace] can be provided to specify which color space the colors should be interpolated in. If [colorSpace] is left null, the colors will be interpolated in the space defined by the starting color in any pairing, unless [reverse] is set to true, in which case they'll be interpolated in the space defined by the ending color.

final palette = <ColorModel>[
  RgbColor(255, 0, 0),
  RgbColor(0, 255, 0),
  RgbColor(0, 0, 255),
];

// [(RgbColor(255, 0, 0), RgbColor(91, 33, 0), RgbColor(0, 255, 0), RgbColor(0, 34, 59), RgbColor(0, 0, 255))]
final newPalette = palette
    .augment(5, colorSpace: ColorSpace.oklab)
    .map<RgbColor>((color) => color.toRgbColor());

The Chroma Value #

The [chroma] getter returns a value that represents the lightness of a color on a 0 to 1 scale.

The value is derived from the color's lightness value in the Oklab color space by normalizing it to a linear curve.

  print(RgbColor(0, 0, 0).chroma); // 0
  print(RgbColor(127, 127, 127).chroma); // 0.5
  print(RgbColor(255, 255, 255).chroma); // 1.0

The [withChroma] method will return a modified color by applying the supplied chroma value to the color in the Oklab color space and converting it back to its original color space.

  final color = RgbColor(42, 176, 232);
  print(color.chroma); // 0.534
  print(color.withChroma(0.3)); // RgbColor(21, 101, 135)