Sentinel-2 L2A True Color Optimized in R and terra

enhanceRGB.R

# Original source: https://custom-scripts.sentinel-hub.com/sentinel-2/l2a_optimized/

enhanceRGB = function(x, maxR = 3, midR = 0.13, sat = 1.2, gamma = 1.8,
                      cores = 1) {

  ## functions -----------------------------------------------------------------
  sAdj = function(a) {
    adjGamma(adj(a, midR, 1, maxR))
  }

  gOff = 0.01
  gOffPow = gOff**gamma
  gOffRange = (1 + gOff)**gamma - gOffPow

  adjGamma = function(b) {
    ((b + gOff)**gamma - gOffPow) / gOffRange
  }

  adj = function(a, tx, ty, maxC) {
    ar = a / maxC
    ar * (ar * (tx / maxC + ty - 1) - ty) / (ar * (2 * tx / maxC - 1) - tx / maxC)
  }

  satEnh = function(r, ...) {
    avgS = mean(terra::global(r, fun = "mean", na.rm = TRUE)[["mean"]])
    f = function(band, ...) {avgS + band * sat}
    r[[1]] = terra::lapp(r[[1]], fun = f, cores = cores)
    r[[2]] = terra::lapp(r[[2]], fun = f, cores = cores)
    r[[3]] = terra::lapp(r[[3]], fun = f, cores = cores)
    r = terra::clamp(r, lower = 0, upper = 1, values = TRUE)
    return(r)
  }

  sRGB = function(c) {
    thresh = 0.0031308
    c = terra::ifel(
      c <= thresh,
      12.92 * c,
      (1.055 * c**0.41666666666) - 0.055
    )
    return(c)
  }

  ## processing ----------------------------------------------------------------
  x = terra::clamp(x, lower = 0, upper = 1, values = TRUE)
  x = terra::app(x, fun = sAdj, cores = cores)
  x = sRGB(satEnh(x, sat))
  return(x)

}