st_rgb {stars}

reduce dimension to rgb (alpha) hex values

Description

reduce dimension to rgb (alpha) hex values

Usage

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

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 by "percent".

stretch

logical or character; if TRUE or "percent", each band is stretched to 0 ... maxColorValue by "percent clip" method using probs values. If "histogram", a "histogram equalization" is performed (probs values are ignored). If stretch is NULL or FALSE, no stretching is performed. Other character values are interpreted as "percent" and a message will be printed.

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. Alternatively, you can use plot.stars with the rgb argument to create a three-band composition.

See Also

st_apply, rgb

Examples

tif = system.file("tif/L7_ETMs.tif", package = "stars")
x = read_stars(tif)
st_rgb(x[,,,3:1])
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()
}
r = st_rgb(x[,,,3:1],
		   probs = c(0.01, 0.99),
		   stretch = "percent")
plot(r)
r = st_rgb(x[,,,3:1],
		   probs = c(0.01, 0.99),
		   stretch = "histogram")
plot(r)