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Map data values or atlas keys to hex colors

Source: R/aaa-generics-colormap.R
calculate_color.Rd

Apply an ieegio_colormap to a vector of values or atlas keys, returning a character vector of hex color strings.

Usage

calculate_color(
  x,
  colormap,
  type = c("auto", "discrete", "continuous"),
  colorspace = NULL,
  keep_alpha = TRUE,
  na = "#00000000"
)

Arguments

x

numeric or integer vector of data values / atlas keys

colormap

an ieegio_colormap object

type

one of "auto" (default), "discrete", "continuous". Auto-detection: integer class or any value outside the 0-1 range maps to discrete; numeric values all within 0-1 map to continuous.

colorspace

override the color space stored in colormap; one of "RGB", "sRGB", "HSV", "HCL", "Lab". NULL (default) inherits from colormap$colorspace.

keep_alpha

logical; if TRUE (default), colors with alpha below 255 are returned as #RRGGBBAA. Set to FALSE to always return #RRGGBB, dropping the alpha channel (needed for formats that do not support alpha in hex).

na

color string used to replace NA inputs in the output; defaults to "#00000000" (transparent black). Set to NA to leave NA inputs as NA in the output.

Value

Character vector of #RRGGBB (or #RRGGBBAA when keep_alpha=TRUE and alpha is below 255) color strings, same length as x.

Examples

# Build a red-to-green color table with 5 stops
ct <- as_ieegio_colortable(data.frame(
  Key = c(1L, 5L),
  R = c(255L, 0L), G = c(0L, 255L), B = c(0L, 0L), A = c(255L, 255L)
))
cm <- as_ieegio_colormap(ct)

# Discrete: Key 0 is always black; intermediate keys are interpolated
calculate_color(c(0L, 1L, 3L, 5L), cm)
#> [1] "#00000000" "#FF0000"   "#807F00"   "#00FF00"  

# Continuous: attach a value-to-scaled lookup and map numeric data
lut <- as_ieegio_lookup(data.frame(Value = c(0, 1), Scaled = c(0, 1)))
cm_cont <- as_ieegio_colormap(ct, lookup = lut)
calculate_color(c(0, 0.25, 0.5, 0.75, 1), cm_cont)
#> [1] "#FF0000" "#BF4000" "#808000" "#40BF00" "#00FF00"

# NA handling: default fills NA with transparent black
calculate_color(c(1L, NA_integer_, 5L), cm)
#> [1] "#FF0000"   "#00000000" "#00FF00"  
# Pass na = NA to keep NA in the output
calculate_color(c(1L, NA_integer_, 5L), cm, na = NA)
#> [1] "#FF0000" NA        "#00FF00"
# Drop alpha channel for formats that do not support it
calculate_color(c(1L, 5L), cm, keep_alpha = FALSE)
#> [1] "#FF0000" "#00FF00"