Package 'qualpalr'

Optimize color palette for color vision deficiency

Description

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.

Usage

autopal(
  n,
  colorspace = "pretty",
  cvd = c("protan", "deutan", "tritan"),
  target = 20
)

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

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.
DIN99d	A matrix of the colors in the DIN99d color space (after power transformations).
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 delta E DIN99d.
min_de_DIN99d	The smallest pairwise DIN99d color difference.

Examples

pal <- autopal(3, cvd = "protan", target = 15)
plot(pal)

---

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

---

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 color space or collection of colors, qualpal() projects these colors to the DIN99d color space, where it generates a color palette from the most visually distinct colors, optionally taking color vision deficiency into account.

Usage

qualpal(
  n,
  colorspace = "pretty",
  cvd = c("protan", "deutan", "tritan"),
  cvd_severity = 0
)

Arguments

n	The number of colors to generate.
colorspace	A color space to generate colors from. Can be any of the following: A list with 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 A character vector of length one specifying one of these predefined color spaces: pretty Tries to provide aesthetically pleasing, but still distinct color palettes. Hue ranges from 0 to 360, saturation from 0.1 to 0.5, and lightness from 0.5 to 0.85. This palette is not suitable for high n pretty_dark Like pretty but darker. Hue ranges from 0 to 360, saturation from 0.1 to 0.5, and lightness from 0.2 to 0.4. rainbow Uses all hues, chromas, and most of the lightness range. Provides distinct but not aesthetically pleasing colors. pastels Pastel colors from the complete range of hues (0-360), with saturation between 0.2 and 0.4, and lightness between 0.8 and 0.9. A matrix of colors from the sRGB color space, each row representing a unique color. A data.frame that can be converted to a matrix via data.matrix
cvd	Color vision deficiency adaptation. Use cvd_severity to set the severity of color vision deficiency to adapt to. Permissible values are "protan", "deutan", and "tritan".
cvd_severity	Severity of color vision deficiency to adapt to. Can take any value from 0, for normal vision (the default), and 1, for dichromatic vision.

Details

The function takes a color subspace in the HSL color space, where lightness and saturation take values from 0 to 1. Hue take values from -360 to 360, although negative values are brought to lie in the range {0, 360}; this behavior exists to enable color subspaces that span all hues being that the hue space is circular.

The HSL color subspace that the user provides is projected into the DIN99d color space, which is approximately perceptually uniform, i.e. color difference is proportional to the euclidean distance between two colors. A distance matrix is computed and, as an additional step, is transformed using power transformations discovered by Huang 2015 in order to fine tune differences.

qualpal then searches the distance matrix for the most distinct colors; it does this iteratively by first selecting a random set of colors and then iterates over each color, 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.

qualpal currently only supports the sRGB color space with the D65 white point reference.

Value

A list of class qualpal with the following components.

HSL	A matrix of the colors in the HSL color space.
DIN99d	A matrix of the colors in the DIN99d color space (after power transformations).
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 delta E DIN99d.
min_de_DIN99d	The smallest pairwise DIN99d color difference.

See Also

plot.qualpal, pairs.qualpal

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, "pretty")

# Adapt palette to deuteranopia
qualpal(5, colorspace = "pretty_dark", cvd = "deutan", cvd_severity = 1)

# Adapt palette to protanomaly with severity 0.4
qualpal(8, colorspace = "pretty_dark", cvd = "protan", cvd_severity = 0.4)

## 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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