R/list.raster.files.R

In spatial.tools: R Functions for Working with Spatial Data

#' Spiders a directory for raster files.
#' 
#' @param path Character. The path to search for raster files.
#' @param pattern Character. A regular expression to limit the files that are tested/returned.
#' @param recursive Logical. Search nested subdirectories within the path?
#' @param return_rasters Logical. Return all proper files as RasterBrick objects (TRUE) or as filenames (FALSE).
#' @param return_bbox Logical. Return a SpatialPolygonsDataFrame with the bounding box geometry and the filenames as data.frame attributes.
#' @param bbox_CRS CRS. If return_bbox==TRUE, the CRS that the output bbox SpatialPolygonsDataFrame should be in.
#' @return A list of filenames (return_rasters=FALSE) or a list of RasterBricks (return_rasters=TRUE) and/or a SpatialPolygonsDataFrame of the bounding boxes (return_bbox==TRUE).
#' @author Jonathan A. Greenberg
#' @seealso \code{\link[raster]{brick}},\code{\link[base]{list.files}}
#' 
#' @details This function searches through a path (potentially recursively), and returns
#' the filename and/or a brick for each file that can be coerced safely to a RasterBrick
#' object.  Note that given different flavors of GDAL, this may return different results
#' for the same directory on different computers.  If a foreach parallel backend has
#' been registered, the spidering will use parallel processing to check each file,
#' potentially speeding it up.
#' 
#' @examples { 
#' search_folder <- system.file("external/", package="spatial.tools")
#' # sfQuickInit() # To potentially speed the search up.
#' list.raster.files(path=search_folder)
#' list.raster.files(path=search_folder,return_rasters=TRUE)
#' # sfQuickStop() 
#' }
#' @import raster
#' @import foreach
#' @export

list.raster.files <- function(path=".",pattern=NULL,recursive=FALSE,return_rasters=FALSE,
		return_bbox=TRUE,bbox_CRS=CRS("+proj=longlat +datum=WGS84 +ellps=WGS84 +towgs84=0,0,0"))
{
	i <- NULL # To pass R CMD CHECK
	rowID <- NULL
	
	# List all files
	all_files <- list.files(path=path,pattern=pattern,recursive=recursive,
			include.dirs=TRUE,full.names=TRUE)
	
	raster_files <- foreach(i=all_files,.packages=c("rgdal","raster")) %dopar%
			{
				safef <- tryCatch(brick(i),error=function(err) return(NULL))
				if(return_rasters)
				{
					if(!is.null(safef)) return(safef) else return(NULL)
				} else
				{
					if(!is.null(safef)) return(i) else return(NULL)
				}
			}
	
		
	raster_files <- raster_files[!sapply(raster_files, is.null)]
		
	output <- list(raster_files=raster_files)

	
	if(return_bbox)
	{
		rowIDs <- seq(raster_files)
		bbox_list <- foreach(raster=raster_files,
						rowID=rowIDs,.packages="spatial.tools",
						.combine=rbind) %dopar%
				{
					if(class(raster)=="character") { raster <- brick(raster) }
					
					bbox_poly <- bbox_to_SpatialPolygons(raster)
					bbox_poly <- spTransform(bbox_poly,bbox_CRS)
					
					rasterfname <- normalizePath(path.expand(filename(raster)))
										
					bbox_df <- data.frame(filename=rasterfname,stringsAsFactors=FALSE)
					rownames(bbox_df) <- as.character(rowID)
					
					bbox_poly_df <- SpatialPolygonsDataFrame(bbox_poly,bbox_df,match.ID=FALSE)
					bbox_poly_df <- spChFIDs(bbox_poly_df,as.character(rowID))
					
					
					return(bbox_poly_df)
				}		
		output$bbox <- bbox_list
	}
	
	return(output)
	
}