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Colour mixtures

Description

These functions allow colours to be mixed in any colour space, eitheradditively (like light) or subtractively (like paint). The infix form%.)% is an alternative foraddmix, and%_/% forsubmix, with the mixing amount being fixed to 1 in these cases.

Usage

addmix(base, mixer, amount = 1, space = NULL)submix(base, mixer, amount = 1, space = NULL)X %.)% YX %_/% Y

Arguments

Value

New colours of class"shade", or a new palette function.

Author(s)

Jon Clayden <code@clayden.org>

Examples

addmix(c("red","green","blue"), "red")submix(c("cyan","magenta","yellow"), "cyan")

Complementary colours

Description

This function returns the complement of its argument, the "opposite" coloursin the specified space.

Usage

complement(shades, space = NULL)

Arguments

Value

New colours of class"shade", or a new palette function.

Examples

complement("cyan")complement("cyan", space="HSV")complement("cyan", space="Lab")

Retrieve the coordinates of a colour vector

Description

This function retrieves the coordinates of a colour vector's elements,within whatever space it is currently defined.

Usage

coords(x, ...)

Arguments

Value

A matrix giving colour coordinates in the relevant space, one colourper row. Columns are typically named.

Author(s)

Jon Clayden <code@clayden.org>

Examples

coords("red")

Simulate colour appearance for dichromats

Description

This functions manipulates colours to simulate the effects of differentkinds of colour blindness, and specifically dichromacy, in which only two ofthe usual three types of photoreceptors are present. There are three types,corresponding to the loss of red, green or blue photoreceptors.

Usage

dichromat(shades, type = c("protanopic", "deuteranopic", "tritanopic",  "none"))

Arguments

Value

New colours of class"shade" in LMS space, representingprojections of the original shades onto a submanifold appropriate to thetype of dichromacy being simulated.

Author(s)

Jon Clayden <code@clayden.org>

References

Brettel, H., Viénot, F. and Mollon, J.D. (1997). Computerized simulation ofcolor appearance for dichromats. Journal of the Optical Society of America A14(10):2647-2655.

Examples

dichromat(c("red", "green", "blue"))

Colour distance

Description

This function calculates a distance measure that aims to quantify theperceptual difference between a vector of colours and a reference colour.The measure in question is the CIE Delta E (2000), which is calculated basedon colour coordinates in Lab space.

Usage

distance(shades, reference)

Arguments

Value

A numeric vector of distances.

Author(s)

Jon Clayden <code@clayden.org>

References

http://www.brucelindbloom.com/index.html?Eqn_DeltaE_CIE2000.html

Examples

distance(c("red","green","blue"), "red")

Colour gradients

Description

This function returns a set of colours interpolating between the specifiedkey colours, equally separated in the specified space.

Usage

gradient(shades, steps = NULL, space = NULL)

Arguments

Details

The key colours may be specified explicitly, or else a built-in colour mapmay be used. The maps available are currently those developed for Python'smatplotlib 2.0, namely"magma","inferno","plasma" and"viridis", and certain ColorBrewer palettes,namely"Blues","Reds","YlOrRd" (yellow-orange-red)and"RdBu" (red-grey-blue, a balanced diverging scale).

Value

A character vector of class"shade" containing the gradientelements in the specified space, or a palette function.

Author(s)

Jon Clayden <code@clayden.org>

References

http://bids.github.io/colormap/ for thematplotlib colour maps;http://colorbrewer2.org for the ColorBrewer ones.

Examples

gradient(c("red","blue"), 5)gradient(c("red","blue"), 5, space="Lab")gradient("viridis", 5)

Query or change colour properties

Description

These functions obtain the value of a colour property, or modify it. Theywill convert between colour spaces as required, but the RGB representationwill be appropriately updated in the result.

Usage

saturation(shades, values = NULL)brightness(shades, values = NULL)lightness(shades, values = NULL)chroma(shades, values = NULL)hue(shades, values = NULL)opacity(shades, values = NULL)delta(...)scalefac(...)recycle(...)

Arguments

Details

Brightness and lightness differ technically, in the sense that one isabsolute and the other is relative. Intuitively, a grey square on whitepaper is brighter under bright sunlight than in a dark room, but itslightness (relative to the white around it) is constant between conditions.In these functions, brightness is “value” in HSV space and is between 0and 1, while lightness is defined in Lab space and is between 0 and 100.Saturation and chroma are also related. Hue is defined in HSV space, withred at 0º (and 360º), which is generally the most familiar parameterisation.

Value

Current colour property values, or new colours of class"shade". Ifshades is a function, the result will be a newfunction that wraps the old one and modifies its return value accordingly.

Note

The colour property functions are vectorised over both of theirarguments, such that the dimensions of the result will bec(length(values),dim(shades)). However, therecycle functioncan be used to suppress the usual dimensional expansion, and insteadfollow R's standard recycling rule.

Author(s)

Jon Clayden <code@clayden.org>

Examples

saturation(c("papayawhip","lavenderblush","olivedrab"))saturation("papayawhip", 0.7)saturation("papayawhip", delta(0.2))saturation("papayawhip", scalefac(1.5))saturation(c("red","green"), c(0.4,0.6))saturation(c("red","green"), recycle(0.4,0.6))

The shade class

Description

Objects of class"shade" are simply standard R character vectorsrepresenting one or more 8-bit (s)RGB colours in CSS-like hex format, butwith extra attributes giving the current colour space and coordinates.

Usage

shade(x, ...)## S3 method for class 'shade'shade(x, ...)## S3 method for class 'color'shade(x, ...)## S3 method for class 'matrix'shade(x, space = "sRGB", alpha = NULL, ...)## S3 method for class 'character'shade(x, ...)## Default S3 method:shade(x, ...)## S3 method for class 'shade'print(x, ...)## S3 method for class 'shade'x[i]## S3 replacement method for class 'shade'x[i] <- value## S3 method for class 'shade'c(...)## S3 method for class 'shade'rep(x, ...)## S3 method for class 'shade'rev(x)## S3 method for class 'shade'x == y## S3 method for class 'shade'x != y## S3 method for class 'equal.shade'all(target, current, hexonly = FALSE, ...)

Arguments

Details

Comparison between"shade" objectsx andy is achievedby convertingy (the second argument) into the colour space ofx and then comparing coordinates, after any clipping.

Value

A character vector of class"shade", with additionalattributes as follows.

Note

When concatenating, shades that are all from the same space willremain in that space, but shades from different spaces will be warped to“XYZ” space.

Author(s)

Jon Clayden <code@clayden.org>

Examples

s <- shade(c("red", "green", "blue"))s[1]s[1] <- "pink"

Retrieve the space of a colour vector

Description

This function retrieves the colour space in which its argument is currentlydefined.

Usage

space(x, ...)

Arguments

Value

A string naming a colour space.

Author(s)

Jon Clayden <code@clayden.org>

Examples

space("red")

Simple colour swatches

Description

This function provides a simple visualisation of a colour series as a seriesof boxes against the specified background colour. If the input has more thanone dimension then the boxes will be arranged in a grid (flattening furtherdimensions after the second).

Usage

swatch(x, bg = "white", ...)

Arguments

Author(s)

Jon Clayden <code@clayden.org>

Examples

swatch(c("red", "green", "blue"))

Shift colours between spaces

Description

This function shifts the current colour space of its arguments to thespecified space, returning a new object of class"shade".

Usage

warp(x, space)

Arguments

Details

Valid names for spaces are currently those supported by theconvertColor function, namely “sRGB”, “Apple RGB”, “CIERGB”, “XYZ”, “Lab” and “Luv”; plus “RGB” (which is treated as analias for “sRGB”), “HSV”, “LCh” and “LMS”. Case is not significant.

Value

A new object of class"shade".

Note

LMS space, used for chromatic adaptation and simulating colourblindness, is not uniquely defined. Here we use the (linearised) Bradfordtransform, obtained by Lam (1985) and used widely in ICC colour profilesand elsewhere, to transform to and from CIE XYZ space.

R uses the D65 standard illuminant as the reference white for the “Lab”and “Luv” spaces.

Author(s)

Jon Clayden <code@clayden.org>

References

Lam, K.M. (1985). Metamerism and colour constancy. PhD thesis, University ofBradford.

See Also

convertColor

Examples

warp("red", "HSV")