Generate a horizontal colorbar image — colorbar

Creates a horizontal colorbar as a 4-channel RGBA array. The color strip and optional tick labels are rendered to PNG using base R graphics (headless-safe). Returns a 3D array suitable for image_to_array() or direct composition.

Usage

colorbar_horizontal(
  colormap,
  n_colors = 256L,
  width = 600L,
  height = 80L,
  ticks = NULL,
  tick_labels = NULL,
  data_range = c(0, 1),
  label_cex = 1,
  title = NULL,
  background = c(1, 1, 1, 1)
)

Arguments

colormap: A vector of colors or a function returning colors (e.g. grDevices::hcl.colors).
n_colors: Number of discrete color segments in the gradient.
width: Output width in pixels.
height: Output height in pixels.
ticks: Numeric vector of tick positions in data units (matching data_range). If NULL, ticks are computed automatically via pretty() restricted to the data range.
tick_labels: Character vector of tick labels. If NULL, defaults to formatted tick values.
data_range: The data range that ticks are specified in. Defaults to c(0, 1).
label_cex: Label size multiplier.
title: Optional title string drawn above the color strip (horizontal) or to the right (vertical).
background: Background RGBA color (0-1 scale).

Value

A 3D array of dimensions (height, width, 4) with values in [0, 1].

Examples

cbar <- colorbar_horizontal(viridis_colormap, data_range = c(-2, 3),
    title = "Value")
dim(cbar)  # height x width x 4
#> [1]  80 600   4