Colour palette from a linear cosine formula

Generates a smoothly varying colour palette using the linear cosine formula described by Iñigo Quilez for procedural palettes (see https://blog.djnavarro.net/posts/2025-09-14_cosine-palettes/): $$f(t) = a + b \cos(2 \pi (c t + d))$$ where \(a = (0.5, 0.5, 0.5)\) is fixed and \(b\), \(c\), \(d\) are each an RGB triple sampled (with replacement) from base.

Usage

palette_cosine(n, base = NULL, seed = 1L)

Arguments

n

A single positive whole number: the number of colours to generate.

base

NULL (the default) or a character vector of candidate colours to sample b, c, and d from. NULL uses grDevices::colors(distinct = TRUE).

seed

A single whole number seeding the random sampling of b, c, and d, so the same seed always produces the same palette.

Value

A character vector of n hex colour strings.

Details

As in the source algorithm, resulting values are clamped only on the high end (values above 1 are capped at 1); values below 0 are folded back with abs() rather than clamped to 0. This is an intentional quirk inherited from the source algorithm, not a bug – it occasionally produces a colour "reflected" around black rather than a flat black.

See also

Other palette helpers: palette_gradient(), palette_harmony(), palette_manual(), palette_tonal(), palette_walk()

Examples

palette_cosine(n = 16, seed = 11)
#>  [1] "#7F1616" "#6F1A17" "#362A20" "#22442F" "#8A6642" "#F18A5A" "#FFAD74"
#>  [8] "#FFCB8F" "#FFE0A9" "#FFE9C0" "#FFE6D3" "#AAD6E1" "#40BDE8" "#1F9CE9"
#> [15] "#6377E3" "#7F54D6"
draw(effect_swatch(color = palette_cosine(n = 16, seed = 11)))