Shades of a single colour

Produces n visually distinct shades of one colour, for when several data series share a carrier and would otherwise be drawn identically.

Usage

energypal_gradient(
  color,
  n = 3,
  spread = 0.1,
  along = c("lightness", "chroma")
)

Arguments

color

A single colour, as hex or any name grDevices::col2rgb() accepts.

n

Number of shades to return (default 3).

spread

How far to spread, roughly in OKLAB lightness units either side of the base (default 0.10). Larger values are more distinguishable but drift further from the carrier's identity.

along

What to vary: "lightness" (default) or "chroma". Hue is never varied — it is what makes the colour recognisable as that carrier.

Value

A character vector of n hex colours, dark to light.

Details

Shades are spread symmetrically around the base colour in OKLAB, a perceptually uniform space, so a given spread looks like the same step whether the colour is near-black coal or bright yellow nuclear. The base colour is always among the results when n is odd.

Hue is held fixed, which is what keeps the shades reading as one carrier. Colours already close to the edge of the sRGB gamut are the exception: making them lighter pushes them outside it, and the clip back into sRGB rotates the hue slightly. Across the built-in palettes the typical rotation is under two degrees, with pale saturated blues the worst at around thirty. Proper gamut mapping is planned but not implemented.

See also

energypal_colors() with gradient = TRUE, which applies this automatically to labels that share a carrier.

Examples

# bright colours no longer collapse
energypal_gradient("#FFD700", n = 5)   # nuclear yellow
#> [1] "#DCB400" "#ECC400" "#FDD500" "#FFE52E" "#FFF648"
energypal_gradient("#2C2C2C", n = 5)   # coal near-black
#> [1] "#141414" "#202020" "#2C2C2C" "#393939" "#464646"

# vary saturation instead
energypal_gradient("#4682B4", n = 3, along = "chroma")
#> [1] "#5F819E" "#4682B4" "#1E82C9"