R/brick_to_array.R

In recolorize: Color-Based Image Segmentation

#' Convert from a RasterBrick to an array
#'
#' Converts from a RasterBrick to a numeric array. Useful
#' in going from patternize to recolorize.
#'
#' @param raster_brick An object of RasterBrick class.
#'
#' @return An image array (probably 1, 3, or 4 channels).
#'
#' @details
#' This function is provided to convert from the RasterBrick objects provided
#' by the alignment functions in the patternize package, e.g. `alignLan`.
#'
#' @export
brick_to_array <- function(raster_brick) {

  # shorter object name
  r <- raster_brick

  # get non-background pixels (> 0) and set them to have alpha = 1
  r[is.na(r)] <- 0
  r_alpha <- r$layer.1 > 0 | r$layer.2 > 0 | r$layer.3 > 0

  # adjust negative values
  r[r < 0] <- 0

  # add alpha layer
  # divide r by 255 so it's in a 0-1 range
  # idk what's going on but here's a weird failsafe:
  r_range <- max(raster::maxValue(r)) - min(raster::minValue(r))
  if (r_range > 255) {
    r2 <- raster::addLayer(r / r_range, r_alpha)
  } else {
    r2 <- raster::addLayer(r / 255, r_alpha)
  }

  # convert to an array
  r3 <- raster::as.array(r2)

  # and return
  return(r3)

}