R/genMosaicList.R

In spatialstatisticsupna/RGISTools: Handling Multiplatform Satellite Images

#' Mosaic a list of raster images
#'
#' \code{genMosaicList} makes a single mosaic from a list of raster images.
#'
#' This is a helper function used by other functions in this package. It combines
#' a list of \code{raster} images with different geolocations. If images overlap,
#' the function applies \code{fun} to calculate the new values for the 
#' overlapping pixels. If not specified, \code{fun = max}.
#'
#' @param imageList \code{list} of \code{RasterLayers}.
#' @param fun the function being applied to pixels that overlap.
#' @param verbose logical argument. If \code{TRUE}, the function prints the 
#' running steps and warnings.
#' 
#' @return a \code{raster} with the mosaicked images.
#'
#' @examples
#' # create simulated rasters
#' img <- matrix(1:16, ncol = 4, byrow = TRUE)
#' r1 <- raster(img)
#' r2 <- r1
#' r3 <- r1
#' extent(r2) <- extent(1, 2, 1, 2)
#' extent(r3) <- extent(1, 2, 0, 1)
#' imageList <- list(r1, r2, r3)
#' # mosaic simulated rasters
#' mr <- genMosaicList(imageList)
#' spplot(mr)
genMosaicList <-function(imageList, fun="max",verbose=TRUE){
  if(length(imageList)>1){
    names(imageList) <- NULL
    imageList$fun<-fun
    imageList$tolerance<-0.000005
    imageList$na.rm <- TRUE
    mosaic <- do.call(mosaic, imageList)
    return(mosaic)
  }else{
    if(verbose){
      warning("There is only one raster image in imgList. No need to merge.")
    }
    return(imageList[[1]])
  }
}