reduce dimension to rgb (alpha) hex values

Source: R/plot.R

reduce dimension to rgb (alpha) hex values

st_rgb(
  x,
  dimension = 3,
  use_alpha = dim(x)[dimension] == 4,
  maxColorValue = 255L,
  probs = c(0, 1),
  stretch = FALSE
)

Arguments

x

object of class stars
dimension

dimension name or number to reduce
use_alpha

logical; if TRUE, the fourth band will be used as alpha values
maxColorValue

integer; maximum value for colors
probs

probability values for quantiles used for stretching
stretch

logical; if TRUE, each band is stretched to 0 ... maxColorValue

Details

the dimension's bands are mapped to red, green, blue, alpha; if a different ordering is wanted, use [.stars to reorder a dimension, see examples

See also

st_apply, rgb

Examples

tif = system.file("tif/L7_ETMs.tif", package = "stars")
x = read_stars(tif)
st_rgb(x[,,,3:1])

#> stars object with 2 dimensions and 1 attribute
#> attribute(s):
#>  L7_ETMs.tif       
#>  Length:122848     
#>  Class :character  
#>  Mode  :character  
#> dimension(s):
#>   from  to  offset delta                       refsys point values x/y
#> x    1 349  288776  28.5 UTM Zone 25, Southern Hem... FALSE   NULL [x]
#> y    1 352 9120761 -28.5 UTM Zone 25, Southern Hem... FALSE   NULL [y]
r = st_rgb(x[,,,c(6,5,4,3)], 3, use_alpha=TRUE) # now R=6,G=5,B=4,alpha=3
if (require(ggplot2)) {
 ggplot() + geom_stars(data = r) + scale_fill_identity()
}