Title: Automatic Generation of Qualitative Color Palettes
Version: 2.0.0
Description: Automatic generation of maximally distinct qualitative color palettes, optionally tailored to color deficiency. A set of colors or a subspace of a color space is used as input and a final palette of specified size is generated by picking colors that maximize the minimum pairwise difference among the chosen colors. Adaptations to color vision deficiency, background colors, and white points are supported.
License: GPL-3
BugReports: https://github.com/jolars/qualpalr/issues
URL: https://jolars.github.io/qualpalr/
Encoding: UTF-8
RoxygenNote: 7.3.2
VignetteBuilder: knitr
SystemRequirements: C++17
Depends: R (≥ 4.0.0)
Imports: graphics, stats, utils, Rcpp
Suggests: randtoolbox (≥ 1.17), testthat, knitr, rmarkdown, maps, rgl, spelling, covr
LinkingTo: Rcpp (≥ 0.12.9)
Language: en-US
NeedsCompilation: yes
Packaged: 2026-01-29 15:31:04 UTC; jola
Author: Johan Larsson ORCID iD [aut, cre]
Maintainer: Johan Larsson <johan@jolars.co>
Repository: CRAN
Date/Publication: 2026-01-29 17:10:07 UTC

qualpalr: Automatic Generation of Qualitative Color Palettes

Description

Automatic generation of maximally distinct qualitative color palettes, optionally tailored to color deficiency. A set of colors or a subspace of a color space is used as input and a final palette of specified size is generated by picking colors that maximize the minimum pairwise difference among the chosen colors. Adaptations to color vision deficiency, background colors, and white points are supported.

Author(s)

Maintainer: Johan Larsson johan@jolars.co (ORCID)

See Also

Useful links:

Analyze a categorical color palette

Description

Analyze a categorical color palette with respect to the differences between the colors in the palette.

Usage

analyze_palette(
  palette,
  cvd = c(protan = 0, deutan = 0, tritan = 0),
  bg = NULL,
  metric = c("ciede2000", "din99d", "cie76")
)

Arguments

palette

Either a matrix of RGB values (with values between 0 and 1), a data frame with RGB values, or a character vector of hex colors.

cvd

Color vision deficiency adaptation. This must be a named vector with names protan, deutan, and tritan and values between 0 and 1, where 0 means no adaptation and 1 means full adaptation.

bg

Background color to consider (but not include) when generating the palette. This is useful to avoid colors that are too close to the background/canvas color. If NULL (the default), the background color is not considered at all. Any color that is convertable via col2rgb is acceptable, including hex colors.

metric

The color metric to use for the color distance matrix.

Value

A list of lists, one for each type of color vision deficiency plus normal vision. Each list contains difference_matrix, min_distances, and bg_min_distance

See Also

qualpal()

Examples

pal <- qualpal(5)
analyze_palette(pal$hex, cvd = c(protan = 1))

Optimize color palette for color vision deficiency

Description

Optimize color palette for color vision deficiency

Deprecated functions in package qualpal.

The functions listed below are deprecated and will be defunct in the next major version future. When possible, alternative functions with similar functionality are also mentioned. Help pages for deprecated functions are available at help("<function>-deprecated").

Usage

autopal(
  n,
  colorspace = list(h = c(0, 360), s = c(0.2, 0.5), l = c(0.6, 0.85)),
  cvd = c("protan", "deutan", "tritan"),
  target = 20
)

autopal

This function is deprecated and will be removed in a future release. No direct replacement is available.

Optimize color palette for color vision deficiency

Description

Deprecated: This function is deprecated and will be removed in a future release. There is no direct replacement.

Arguments

n

Number of colors to generate.

colorspace

Either 1) a list of three named numeric vectors: h (hue), s (saturation), and l (lightness), all of length 2 specifying a min and max value for the range. The values has to be in the range -360 to 360 for h, and 0 to 1 for s and l 2), or 2) a character vector specifying one of the predefined color spaces (see below).

cvd

Color vision deficiency adaptation to adapt the color palette to.

target

Target color difference.

Details

This function adapts color palettes to color vision deficiency (CVD) by optimizing the CVD severity to try reach a target color difference (DIN99d \delta E) of the user's choosing. Basically, it will choose a color palette that is as close as possible to the target \delta E by tweaking the CVD severity option in qualpal.

The rationale for this function is that when there are few colors in a color palette, there is no cost involved in adapting colors to CVD – the colors will still remain distinct. As more an more colors are added to the palette, however, adapting the color palette to CVD will eventually lead to colors that are too similar. This function gradually loosens the adaptation to CVDs by lowering the severity of CVD to simulate to before picking colors (the cvd_severity argument in qualpal)

Value

A list of class qualpal with the following components.

HSL

A matrix of the colors in the HSL color space.

RGB

A matrix of the colors in the sRGB color space.

hex

A character vector of the colors in hex notation.

de_DIN99d

A distance matrix of color differences according to the metric used. The name is misleading, bu kept for backwards compatibility.

hex

A character vector of the colors in hex notation.

min_de_DIN99d

The minimum pairwise DIN99d color difference among all colors in the palette.

See Also

qualpal-deprecated

Convert colors between colorspaces

Description

Convert colors between colorspaces

Usage

convert_colors(colors, from, to)

Arguments

colors

A matrix of colors

from

The colorspace of the input colors, one of "rgb", "hsl", "din99d", "lab", "xyz"

to

The colorspace of the output colors, one of "rgb", "hsl", "lab", "xyz"

Value

The colors converted to the new colorspace

Retrieve one of the built-in color palettes

Description

This function retrieves a color palette from the built-in palettes. To see the available palettes, use list_palettes().

Usage

get_palette(palette = "ColorBrewer:Accent")

Arguments

palette

A character string specifying the name of the color palette to

Value

A character vector of colors in hex format.

See Also

list_palettes()

Examples

get_palette("Vermeer:LittleStreet")

List available color palettes

Description

List available color palettes

Usage

list_palettes()

Value

A list of available color palettes. Each palette is a named list with a character vector.

See Also

qualpal()

Examples

list_palettes()

Scatterplot matrix of qualitative color palette

Description

Plots the colors in an object of class "qualpal" as a scatterplot matrix on either the DIN99d (the default) or HSL color space.

Usage

## S3 method for class 'qualpal'
pairs(x, colorspace = c("DIN99d", "HSL", "RGB"), ...)

Arguments

x

A list object of class "qualpal" generated from qualpal.

colorspace

The color space in which to plot the colors ("DIN99d", "HSL", or "RGB").

...

Arguments to pass on to pairs.

See Also

qualpal, plot.qualpal, pairs

Examples

col_pal <- qualpal(3)
pairs(col_pal)
pairs(col_pal, colorspace = "HSL")

Multidimensional scaling map of qualitative color palette

Description

Uses the colors in a qualpal object to compute and plot a multidimensional scaling (MDS) map using cmdscale on the Delta E DIN99d distance matrix.

Usage

## S3 method for class 'qualpal'
plot(x, ...)

Arguments

x

An object of class "qualpal" generated from qualpal.

...

Arguments to pass on to plot.

See Also

qualpal, pairs.qualpal, plot

Examples

col_pal <- qualpal(3)
plot(col_pal)

Print qualpal palette

Description

Print the result from a call to qualpal.

Usage

## S3 method for class 'qualpal'
print(x, colorspace = c("HSL", "DIN99d", "RGB"), digits = 2, ...)

Arguments

x

An object of class "qualpal".

colorspace

Color space to print colors in.

digits

Number of significant digits for the output. (See print.default.) Setting it to NULL uses getOption("digits").

...

Arguments to pass to print.default.

Value

Prints the colors as a matrix in the specified color space as well as a distance matrix of the color differences. Invisibly returns x.

Examples

f <- qualpal(3)
print(f, colorspace = "DIN99d", digits = 3)

Generate qualitative color palettes

Description

Given a collection of colors, qualpal() algorithmically tries to select to n most distinct colors from the provided input colors, optionally taking color vision deficiency into account.

Usage

qualpal(
  n,
  colorspace = list(h = c(0, 360), s = c(0.2, 0.5), l = c(0.6, 0.85)),
  cvd = c(protan = 0, deutan = 0, tritan = 0),
  cvd_severity,
  bg = NULL,
  metric = c("ciede2000", "din99d", "cie76"),
  extend = NULL,
  white_point = c("D65", "D50", "D55", "A", "E")
)

Arguments

n

The number of colors to generate.

colorspace

A color space to generate colors from. Can be any of the following:

  • A list that describes a color space in either HSL or LCHab color space. In the first case (HSL), the list must contain the following named vectors, each of length two, giving a range for each item.

    h

    Hue, in range from -360 to 360

    s

    Saturation, in the range from 0 to 1

    l

    Lightness, in the range from 0 to 1

    In the second case (LCHab), the list must contain the following named vectors, each of length two, giving a range for each item.

    h

    Hue, in range from -360 to 360

    c

    Chroma, in the range from 0 to infinity

    l

    Lightness, in the range from 0 to 100

    In these cases, qualpal() will generate

  • A character vector of length one in the form of "Source:Palette", where Domain is the name of a source that provides a color palette, and Palette is the name of a color palette from that source. See list_palettes() for available palettes.

  • A matrix or data frame of RGB values (with values between 0 and 1).

cvd

Color vision deficiency adaptation. This must be a named vector with names protan, deutan, and tritan and values between 0 and 1, where 0 means no adaptation and 1 means full adaptation.

cvd_severity

DEPRECATED. Use a named cvd vector instead, e.g. c(protan = 0.5, deutan = 0.2, tritan = 0).

bg

Background color to consider (but not include) when generating the palette. This is useful to avoid colors that are too close to the background/canvas color. If NULL (the default), the background color is not considered at all. Any color that is convertable via col2rgb is acceptable, including hex colors.

metric

The color metric to use for the color distance matrix.

extend

A palette of colors to use as a fixed set of initial colors in the palette, which can be either a matrix or data frame of RGB values (with values between 0 and 1) or a character vector of hex colors (or any other format that's acceptable in grDevices::col2rgb()).

white_point

The white point to use for color space conversions. Can be one of "D65" (default, daylight at 6500K), "D50" (daylight at 5000K), "D55" (daylight at 5500K), "A" (incandescent tungsten at 2856K), or "E" (equal energy).

Details

The main idea is to compute a distance matrix from all the input colors, and then try to select the most distinct colors based on the color differences between them. It does this iteratively by first selecting the first n colors from the input colors, then iterates over the palette, putting colors back into the total set and replaces it with a new color until it has gone through the whole range without changing any of the colors.

Optionally, qualpal can adapt palettes to cater to color vision deficiency (CVD). This is accomplished by taking the colors provided by the user and transforming them to colors that someone with CVD would see, that is, simulating CVD qualpal then chooses colors from these new colors.

Value

A list of class qualpal with the following components.

HSL

A matrix of the colors in the HSL color space.

RGB

A matrix of the colors in the sRGB color space.

hex

A character vector of the colors in hex notation.

de_DIN99d

A distance matrix of color differences according to the metric used. The name is misleading, bu kept for backwards compatibility.

hex

A character vector of the colors in hex notation.

min_de_DIN99d

The minimum pairwise DIN99d color difference among all colors in the palette.

See Also

plot.qualpal(), pairs.qualpal(), list_palettes()

Examples

# Generate 3 distinct colors from the default color space
qualpal(3)

# Provide a custom color space
qualpal(n = 3, list(h = c(35, 360), s = c(0.5, 0.7), l = c(0, 0.45)))

qualpal(3, "ColorBrewer:Set2")

# Adapt palette to deuteranopia
qualpal(5, "ColorBrewer:Dark2", cvd = c(deutan = 1))

# Adapt palette to protanomaly with severity 0.4
qualpal(8, cvd = c(protan = 0.4))

# Generate and extend a palette with 3 colors, using the DIN99d
# metric
pal <- qualpal(3)
qualpal(5, extend = pal$hex, metric = "din99d")

# Use a different white point (D50, common in printing)
qualpal(5, white_point = "D50")

## Not run: 
# The range of hue cannot exceed 360
qualpal(3, list(h = c(-20, 360), s = c(0.5, 0.7), l = c(0, 0.45)))

## End(Not run)

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