[R-sig-Geo] Using RGDAL to "copy" header information... (Jonathan Greenberg)

[Robert Hijmans]

Jonathan

You might be interested in the raster package available from r-forge
(within the Rgis project). You would need to download, build and
install it 'manually'

The below code example reads a line from an input raster, puts the values

library(raster)
infile="d:/input.tif"
outfile="d:/test.grd"
rin <- raster.from.file(infile)
rout <- set.raster(rin, outfile)

for (r in 1:nrow(rin)) {
  rin <- read.row(rin, r)

  rout <- set.values.row(rout, values(rin) + 10, r)
  rout <- write.row(rout)
}



outfile_ext='.bil'
> outfile=paste(outfile_base,outfile_ext,sep='')
> outcon <- file(outfile, "wb")



>
> Message: 2
> Date: Wed, 05 Nov 2008 09:18:47 -0800
> From: Jonathan Greenberg <greenberg at ucdavis.edu>
> Subject: [R-sig-Geo] Using RGDAL to "copy" header information...
> To: gdal-dev at lists.osgeo.org, R-sig-Geo at stat.math.ethz.ch,
>        r-help at r-project.org
> Cc: Solomon Dobrowski <solomon.dobrowski at cfc.umt.edu>
> Message-ID: <4911D577.2050300 at ucdavis.edu>
> Content-Type: text/plain; charset=ISO-8859-1; format=flowed
>
> R-geographers...
>
> I'm trying to solve a problem to implement a line-by-line tiled
> processing using RGDAL (read 1 line of an image, process the one line,
> write one line of the image to a binary file).  Everything except for
> the final step I'm able to do using a combination of RGDAL and r-base
> commands.  Below is the basic structure, the input file "elev" can be
> any image file GDAL supports -- the code below just "copies" the image
> one line at a time:
>
> ###
>
> library(rgdal)
> infile='elev'
> outfile_base='testout'
> outfile_ext='.bil'
> outfile=paste(outfile_base,outfile_ext,sep='')
> outcon <- file(outfile, "wb")
>
> infile_info=GDALinfo(infile)
> nl=infile_info[[1]]
> ns=infile_info[[2]]
>
> for (row in 1:nl) {
>    templine <- readGDAL(infile,region.dim=c(1,ns),offset=c(row-1,0))
>    writeBin(templine[[1]], outcon,size=4)
> }
> close(outcon)
> # Below doesn't work
> # writeGDAL(templine,outfile_base,drivername='EHdr',type="Float32")
>
> ###
>
> The issue is this: I need to be able to effectively copy the
> geographic/header information from the input file (the last line almost
> works, but as you can see it sets the line #s to 1, not "ns"), and parse
> it over to the output file (which is some form of a flat binary file --
> in this case, an Arc Binary Raster, but an ENVI binary output would also
> be good) -- ideally I'd like to be able to modify this header,
> particularly the number type (e.g. if the input file is an integer, and
> I'm writing out a floating point binary, I need that reflected in the
> output header).  I can do this by *manually* creating the output header
> via a series of ascii-writes, but I was wondering if there is a more
> effective way of doing this using RGDAL that might apply generically to
> the header of any binary image file I might write?  Thanks!
>
> --j
>
>
> --
>
> Jonathan A. Greenberg, PhD
> Postdoctoral Scholar
> Center for Spatial Technologies and Remote Sensing (CSTARS)
> University of California, Davis
> One Shields Avenue
> The Barn, Room 250N
> Davis, CA 95616
> Cell: 415-794-5043
> AIM: jgrn307, MSN: jgrn307 at hotmail.com, Gchat: jgrn307
>
>
>