[gdal-dev] Using RGDAL to "copy" header information...

[Jonathan Greenberg]

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