Tools to manage colors for visualizations

This module provides access to color schemes for

• qualitative (or categorical) data: qualitative_colors()

• sequential data: sequential_colors()

• diverging data: diverging_colors()

as explained at https://personal.sron.nl/~pault/

Color schemes are provided through three functions, all accepting the number of different values as first argument. While py:func`sequential_colors` is limited to at most 9 values and py:func`diverging_colors` to at most 11, py:func`qualitative_colors` works with any number of values - but will use different ways to create the scheme depending on the number of values.

clldutils.color.diverging_colors(n)

Between 3 and 11 diverging colors

See also

https://personal.sron.nl/~pault/#sec:diverging

clldutils.color.qualitative_colors(n, set=typing.Optional[str])

Choses n distinct colors suitable for visualizing categorical variables.

See also

https://en.wikipedia.org/wiki/Categorical_variable

Depending on n (and set), different algorithms to compute the colors are chosen:

• n <= 11 and set == ‘boynton’: Colors are chosen according to “Eleven colors that are almost never confused.” by R. M. Boynton, 1989.

• n <= 12 and set == ‘tol’: Colors are chosen according to https://personal.sron.nl/~pault/colourschemes.pdf

• n <= 22: Kenneth Kelly’s “22 colours of maximum contrast” are chosen (as reported by Paul Green-Armytage in https://eleanormaclure.files.wordpress.com/2011/03/colour-coding.pdf)

• else: Recipe taken from https://stackoverflow.com/a/13781114

Parameters:

• n (int) – number of distinct colors to return

• set (str) – name of a particular color set to choose from. “boynton” works for n<=11 and will choose from “Eleven colors that are almost never confused”; “tol” works for n<=12 and will choose from Paul Tol’s qualitative color scheme.

Return type:

typing.List[str]

Returns:

list of n hex color codes

clldutils.color.sequential_colors(n)

Between 3 and 9 sequential colors.

See also

https://personal.sron.nl/~pault/#sec:sequential

clldutils.color.brightness(color)

Compute the brightness of a color specified as RGB triple (or Hex triplet).

See also

https://www.w3.org/TR/AERT/#color-contrast

Parameters:

color (typing.Union[str, list, tuple]) –

Return type:

float

clldutils.color.is_bright(color)

Compute whether a color is considered bright or not.

Note

A brightness value of 125 seems to be a common cut-off above which to regard a color as “bright”.

Parameters:

color (typing.Union[str, list, tuple]) –

Return type:

bool

clldutils.color.rgb_as_hex(s)

Convert a RGB triple to a HEX triplet

Parameters:

s (typing.Union[str, list, tuple]) –

Return type:

str