Functions for rescaling a multiband rasterstack or raster layer to an arbitrary range

rescale_rasters.R

# Functions for rescaling layers/stacks
## Cleaned up/edited the source code for sdvmspecies library (https://cran.r-project.org/web/packages/sdmvspecies/index.html)

rescaleLayer <- function(raster.layer) {
  new.min <- 0; new.max <- 1 ## change for different output range (e.g. 0-255)
  min.value <- cellStats(raster.layer, min, na.rm = TRUE)
  max.value <- cellStats(raster.layer, max, na.rm = TRUE)
  raster.layer <- new.min + (raster.layer - min.value) * ((new.max - new.min) / (max.value - min.value))
  return(raster.layer)
}

rescaleStack <- function(raster.stack) {
  raster.name <- names(raster.stack)
  raster.stack.list <- lapply(X = raster.name, FUN = function(name, raster.stack) {
    return(rescaleLayer(raster.stack[[name]]))}, raster.stack)
  result.stack <- stack(raster.stack.list)
  names(result.stack) <- raster.name
  return(result.stack)
}

rescale <- function(raster.object) {
  if (!(class(raster.object) %in% c("RasterLayer", "RasterStack"))) {
    stop("raster.object needs to be a RasterLayer or RasterStack object!\nraster.object is a ", class(raster.object)[1])
  }
  if (class(raster.object) %in% "RasterLayer") {
    raster.object <- rescaleLayer(raster.object)
  } else {
    raster.object <- rescaleStack(raster.object)
  }
  return(raster.object)
}

## Example ##
# library(raster)
# slogo <- stack(system.file("external/rlogo.grd", package="raster")) 
# plot(slogo, col = topo.colors(101))
# 
# ## rescale a raster stack
# slogoRS <- rescale(slogo)
# plot(slogoRS, col = topo.colors(101))
# 
# ## rescale a single layer
# slogo_1_rs <- rescale(slogo[[1]])
# plot(slogo_1_rs, col = topo.colors(101))
# 
# ## fails
# slogoB <- brick(slogo)
# slogoB_RS <- rescale(slogoB)