modCol {plotwidgets}

Modify colors

Description

Modify colors by shading, saturating and changing hue

Usage

modCol(col, darken = 0, saturate = 0, modhue = 0)

saturateCol(col, by = 0)

darkenCol(col, by = 0)

modhueCol(col, by = 0)

contrastcol(col, alpha = NULL)

Arguments

col

a character vector of colors (palette) to modify – a character vector

darken

Use negative values to lighten, and positive to darken.

saturate

Use negative values to desaturate, and positive to saturate

modhue

Change the hue by a number of degrees (0-360)

by

parameter for the saturateCol, darkenCol and modhueCol functions

alpha

alpha value (from 0, transparent, to 255, fully opaque)

Details

This function use the HSL (hue, saturation, luminosity) scheme to modify colors in a palette.

modCol is just a wrapper for the other three functions allowing to modify three parameters in one go.

saturateCol, darkenCol and modhueCol modify the saturation, luminosity and hue in the HSL color model.

contrastcol() returns black for each light color (with L > 0.5) and white for each dark color (with L < 0.5).

Value

a character vector containing the modified palette

Functions

• saturateCol: Change the saturation of a color or palette by a fraction of "by"

• darkenCol: Modify the darkness of a color or palette (positve by - darken, negative by – lighten)

• modhueCol: Modify the hue of a character vector of colors by by degrees

• contrastcol: Return white for dark colors, return black for light colors

Examples

plot.new()
## Loop over a few saturation / lightess values
par(usr=c(-0.5, 0.5, -0.5, 0.5))
v <- c(10, 9, 19, 9, 15, 5)
pal <- plotPals("zeileis")
for(sat in seq.int(-0.4, 0.4, length.out=5)) {
  for(lgh in seq.int(-0.4, 0.4, length.out=5)) {
    cols <- saturateCol(darkenCol(pal, by=sat), by=lgh)
    wgPlanets(x=sat, y=lgh, w=0.16, h=0.16, v=v, col=cols)
  }
}
axis(1)
axis(2)
title(xlab="Darkness (L) by=", ylab="Saturation (S) by=")

## Now loop over hues
a2xy <- function(a, r=1, full=FALSE) {
  t <- pi/2 - 2 * pi * a / 360
  list( x=r * cos(t), y=r * sin(t) )
}

plot.new()
par(usr=c(-1,1,-1,1))
hues <- seq(0, 360, by=30)
pos <- a2xy(hues, r=0.75)
for(i in 1:length(hues)) {
  cols <- modhueCol(pal, by=hues[i])
  wgPlanets(x=pos$x[i], y=pos$y[i], w=0.5, h=0.5, v=v, col=cols)
}

pos <- a2xy(hues[-1], r=0.4)
text(pos$x, pos$y, hues[-1])