evercoder/culori

A comprehensive color library for JavaScript.

culori's Issues

HSV parse error on achromatic color

GLHS: a generalized lightness, hue, and saturation color model

Should `flags` be enumerable?

Arguments for enumerable

• Extending a color with { ...color } maintains the flags.

Arguments against enumerable

• Cleaner output in the console and tests. (although tests will need to check the flags separately, for better coverage)
• May be that extending a color with { ...color } will result in inaccurate flags.

Check interpolation between more than two colors

.css() and .css4() methods

natural spline interpolation does not work with two values

Check LCH interpolation for specific examples

blue, green, 8 colors: https://beta.observablehq.com/@danburzo/culori-scales-test

lrgb()

displayable() and clamp()

difference()

css4()

Like css but outputs to the formats defined in Color Module Level 4.

interpolate()

interpolate(color_array, mode = 'rgb') returns an interpolator function that takes an argument [0, 1].

Scales / Interpolators

Direct conversion pairs for HSL / HSV / HSI

HWB

• css hwb parser
• hwb_to_rgb converter
• rgb_to_hwb converter

Direct linear rgb ↔ XYZ d50 conversion matrices

css() can't be invoked in Array.map()

because the index will be passed as the second parameter

Spline interpolation + number/hue/alpha interpolation

For linear interpolation:

• Bring back short vs. long hue interpolation
• Check hue normalization throughout the hue() method

For spline interpolation:

• Add closed version
• How to spline-interpolate alpha?
• How to spline-interpolate short vs long hue?

• need to check that performance was not degraded with current developments...

Monotone cubic interpolation

distance()

Simple, Euclidean distance + read up on these: http://bl.ocks.org/mourner/8a3968f74da743a754af

Add CIE2000 (and possibly CMC) distance

LCh interpolation with achromatic colors

luminance() and contrast()

L = 0.2126 * R + 0.7152 * G + 0.0722 * B in LRGB space.

contrast = (L1 + 0.05) / (L2 + 0.05) in the WGAG spec.

Long vs. short hue interpolation

...in both linear and spline interpolators. Also need to check for correct hue normalization before and after the process.

Check HSL/HSV/HSI interpolation for specific cases

e.g. red to blue https://beta.observablehq.com/@danburzo/culori-scales-test

ColorBrewer

Gray

• gray css parser
• gray_to_rgb converter
• rgb_to_gray converter

Pick a suitable internal format

Regardless of the various formats the colors come in, they ultimately reflect a RGB(A) value, so it makes sense to keep the internal format as R, G, B, A (floating-point values): in -> RGBA -> out

However, for the purposes of color scales, one might have three colors defined:

H - 120, S, L, A
H, S, L, A
H + 120, S, L, A

In which case H could go beyond [0, 360] and we need to store the original value to properly interpolate.

HSLuv color space

http://www.hsluv.org/

Transpile build with Babel

brighten(k)

Benchmark: correctness

parseHex via parseNumber bugs

Make it easy to add new color spaces

e.g. https://github.com/acterhd/hcg-color

Currently, parsers cannot be added - let's have string parsing match CSS Color Level 4.
Converters can be created, but they can't be registered, so we need an API for that.

matplotlib colormaps

https://bids.github.io/colormap/
https://github.com/BIDS/colormap/blob/master/colormaps.py

[interpolate] Open/Closed spline interpolation

• b-spline
• natural spline

Reading material:

• https://www.mathworks.com/help/curvefit/cscvn.html
• G. Koloskov, "Closed natural splines: An effective solution"
• E.T.Y. Lee, "Choosing nodes in parametric curve interpolation"

LCH

• lch css parser
• lch_to_rgb converter
• rgb_to_lch converter

HSL parser normalize without passing through RGB?

Perceptual Rainbow

https://mycarta.wordpress.com/2013/02/21/perceptual-rainbow-palette-the-method/
https://bl.ocks.org/mbostock/310c99e53880faec2434

Further reading

https://www.vis4.net/blog/2011/12/avoid-equidistant-hsv-colors/#picker

swatches()

swatches(interpolator, no_of_colors) to generate color scales.

scale(colors, mode, no_of_colors) can be implemented as swatches(interpolate(colors, mode), no_of_colors).

Normalize hue to 0-360

Make rgb parsers stricter

don't allow mix of percentages and numbers.

Benchmark: format back-forth maintains color

Add spline interpolation

With closed and open variants, like in D3. the closed version can be useful for radial sliders for hue.

LAB

• lab css parser
• lab_to_rgb converter
• rgb_to_lab converter

[nearest] Use v-p trees for better performance?

Use a v-p tree to index() a set of colors based on a specific difference() to enable queries of the type: what are the closest colors in the index to a given color?

Reference: http://pnylab.com/papers/vptree/main.html

Example JS implementation: https://github.com/fpirsch/vptree.js

CAM16 / CAT16 / CAM16-UCS

https://github.com/d3/d3-cam16
https://github.com/connorgr/d3-cam02
http://gramaz.io/d3-cam02/

HSI

• hsi_to_rgb converter
• rgb_to_hsi converter

Cubehelix

• cubehelix_to_rgb converter
• rgb_to_cubehelix converter