hsluv 1.0.0

Dart port of HSLuv.

HSLuv for Dart & Flutter

Dart port of HSLuv (revision 4) with a Flutter sample. This was a direct conversion of the reference implementation.

HSLuv is a human-friendly alternative to HSL.

Color spaces used widely for computer display, such as standard Red Green Blue (sRGB) (and the color models built on it like HSL and HSV) are irregular, which means that even though they have evenly spaced hue values, the corresponding effect is not linear to the human eye.

The CIELUV color space was designed for perceptual uniformity, based on human experiments, and was adopted in 1976 by the International Commission on Illumination (CIE) as a simple-to-compute transformation of the 1931 CIE XYZ color space. CIELUV has been extensively used for applications such as computer graphics which deal with colored lights. When accessed by polar coordinates, CIELUV becomes functionally similar to the HSL color space, with the problem that its chroma component doesn't fit into a specific range. Even though CIELUV and CIELAB color spaces are based on human perception, they are not intuitive when working in code.

By extending CIELUV with a new saturation component, HSLuv allows spanning all of the available chroma as a neat percentage. The HSLuv project is one of the more recent attempts at making these color spaces more intuitive. It allows you to use the CIELUV color space in the same dimensions as the HSL color model.

Designing Color Spaces / Wikipedia article

TL;DR: It is like HSL, but color will only get perceptually lighter or darker when changing the Lightness value. In HSL, if you go from a green hue to a red one, there will be big differences in the perceived lightness. In HSLuv, almost none.

This make it great when building acessible color systems.

Example app showing HSV (top) vs HSLuv (bottom). See how the perceived lightness changes as the hue slider moves.

Usage

In the pubspec.yaml of your flutter project, add the following dependency:

dependencies:
  hsluv: ^VERSION

In your project you can use it in two different ways, either low level (directly accessing values as a list<double>) or high level (similar to HSLColor). HSLuvColor is easier to use, but has less flexibility than a raw list.

import 'package:hsluv/Hsluv.dart';

void main() {
  
  // Low level usage.
  final List<double> hsluvLow = Hsluv.rgbToHsluv([0.2,0.5,0.7]);
  print(Hsluv.hsluvToHex(hsluvLow));

  // High level usage.
  final hsluvFromColor = HSLuvColor.fromColor(Colors(0xffef3e4a));
  print(hsluvFromColor.toString());

  final hsluvFromHSL = HSLuvColor.fromHSL(300, 70, 60);
  print(hsluvFromHSL.toString());
}

Color values ranges

• RGB values are ranging in [0...1]
• HSLuv and HPLuv values have different ranging for their components
  • H : [0...360]
  • S and L : [0...100]
• LUV has different ranging for their components
  • L* : [0...100]
  • u* and v* : [-100...100]
• LCh has different ranging for their components
  • L* : [0...100]
  • C* : [0...?] Upper bound varies depending on L* and H*
  • H* : [0...360]
• XYZ values are ranging in [0...1]

Important: Flutter's HSLColor has lightness and saturation ranging from 0 to 1.0. HSLuv uses 0 to 100. HSInter from the sample tries to mitigate this.

API functions

Note

The passing/returning values, when not String are List<double> containing each component of the given color space/system in the name's order :

• RGB : [red, blue, green]
• XYZ : [X, Y, Z]
• LCH : [L, C, H]
• LUV : [L, u, v]
• HSLuv/HPLuv : [H, S, L]

Function listing

• xyzToRgb(List<double> tuple)
• rgbToXyz(List<double> tuple)
• xyzToLuv(List<double> tuple)
• luvToXyz(List<double> tuple)
• luvToLch(List<double> tuple)
• lchToLuv(List<double> tuple)
• hsluvToLch(List<double> tuple)
• lchToHsluv(List<double> tuple)
• hpluvToLch(List<double> tuple)
• lchToHpluv(List<double> tuple)
• lchToRgb(List<double> tuple)
• rgbToLch(List<double> tuple)
• hsluvToRgb(List<double> tuple)
• rgbToHsluv(List<double> tuple)
• hpluvToRgb(List<double> tuple)
• rgbToHpluv(List<double> tuple)
• hsluvToHex(List<double> tuple)
• hpluvToHex(List<double> tuple)
• hexToHsluv(String s)
• hexToHpluv(String s)
• rgbToHex(List<double> tuple)
• hexToRgb(String hex)

Completely unrelated

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Reporting Issues

Issues and Pull Requests are welcome. You can report here.

License

Copyright 2019 Bernardo Ferrari

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.