@stonecypher/hsluv.ts

What is this?

Chances are you already know what HSLuv (formerly aka HuSL) is if you're
here, but if not, HSLuv is a color scale meant to be easy for humans to
interpret. This package primarily exists to implement
two color spaces: HSLuv and HPLuv. However, in the process, we also
implement transformations for rgb in numeric, rgb in hex strings, hsl,
xyz, luv, and lch, as well as the lightness to y channel transform in
both directions.

$3

What's interesting about HSLuv is that the apparent brightness is normalized.
If you've tried to pick color palettes in the regular HSL space, you've
probably noticed that at the same lightness, the colors in the blue end of the
hue appear far darker than the colors in the yellow end.

HSLuv fixes that. For any given hue, the apparent brightness of a given
lightness is meant to be simiar (using a whole bunch of complicated math and
human measurement.)

From Alexei's page,

$3

The downside of HSLuv is that there are colors it can't represent. There is
no blue with the apparent brightness of canary yellow.

HPLuv makes these work by sacrificing saturation correctness. HPLuv will
always produce a color, but sometimes a less satisfying one than HSLuv.

How to use

``
npm install --save-dev @stonecypher/hsluv.ts
`

`typescript
import { hsluv_to_hex, hsluv_to_rgb, hex_to_hsluv } from '@stonecypher/hsluv.ts';

console.log( hsluv_to_hex([ 250, 50, 50 ]) );
// prints "#5c78a5"

console.log( hsluv_to_rgb([ 250, 50, 50 ]) );
// prints [ 0.35957778969721066, 0.4708793745621595, 0.6462180065016022 ]

console.log( hex_to_hsluv('#5c78a5') );
// prints [ 250.2650513570262, 49.70313649414815, 50.00687151772391 ]
`

API

The following functions are exposed.

All functions take two arguments, according to the types in their names.

* rgb_to_hsluv
* rgb_to_hpluv
* hsluv_to_rgb
* hpluv_to_rgb
* hex_to_hsluv
* hex_to_hpluv
* hsluv_to_hex
* hpluv_to_hex
* lch_to_hsluv
* lch_to_hpluv
* hsluv_to_lch
* hpluv_to_lch
* rgb_to_xyz
* xyz_to_rgb
* rgb_to_lch
* lch_to_rgb
* luv_to_xyz
* xyz_to_luv
* luv_to_lch
* lch_to_luv
* l_to_y
* y_to_l
* hex_to_rgb

$3

* l and y are numbers.
* hex is a seven-character string starting with #.
* The library consumes upper and lower case, but produces lower case.
* hsl and hpl are a tuple (array) of range [0;360], [0;100], [0;100]
* rgb is a tuple of range [0;1], [0;1], [0;1]
* xyz, lch, and luv are a tuple of three unbounded signed numbers

Bundling

This implementation provides .d.ts for Typescript, es6 native tree-shakeable
for most work, es6 commonjs bundled for quick work, es6 iife for in-browser
learning and debugging, and es6 iife minified for bandwidth-sensitive
prepackaged deployment like CDNs. main refers to es6 cjs, and module
refers to es6 native tree-shakeable.

Quality

This implementation passed the author's 24,000
tests.
By comparison to the reference implementation, calculations are accurate to
within 1 in 10¹⁵,
which the author says is fine.

This implementation is CI tested
under Node 8,12,13 on Windows, Mac, and Ubuntu.

Changes

* Typescript.
* Names are now in snake_case instead of camelCase.
* Many tests were added in the name of code coverage.
* CI under Github Actions

Wait, are there two of these?

I made this because Typescript wasn't on the author's somewhat extensive
language list, and because the Haxe tooling wasn't very convenient under
rollup`. When I was done and tried to publish, I realized someone else
already had done this, and even used
the same name I did; it was just missing from the author's list.

However, my approach to typing, packaging, and tooling is mildly different than
theirs, so I'm gonna publish anyway. Besides, it's already finished (sigh 😞,)
and I like some of the differences in mine between these two projects.