[R-sig-Geo] Writing a tif using rgdal

[Tim Keitt]

I seem to remember writing a wrapper for the gdal copy function,
although none of that has be extensively tested. If you copy an existing
dataset to a writable dataset, you could then retrieve the data, operate
on it and write back to the new dataset. It should (?) then have all the
metadata copied from the original. Sorry, I didn't see in your code
where you were overwriting gdal pointers.

THK

On Tue, 2006-02-07 at 20:19 +0100, Roger Bivand wrote:
> On Tue, 7 Feb 2006, Andy Bunn wrote:
> 
> > Howdy List:
> > 
> > I'm reading in a large number of satellite images and analyzing them in R. I
> > know how to read a tif into R using rgdal and manipulate it. Is there a good
> > way to write a new tif out using the projection data from the original?
> > 
> > So in the example below how can I write out z as a jpg using the metadata
> > and such from x?
> > 
> > -Andy
> > 
> > 
> > library(rgdal)
> > logo <- system.file("pictures/Rlogo.jpg", package="rgdal")[1]
> > x <- new("GDALReadOnlyDataset", logo)
> > displayDataset(x)
> > y <- getRasterData(x)
> > z <- rowMeans(y, dims=2)
> > dim(z)
> 
> Taking a deep breath and remembering to do save.image() frequently 
> [overwriting GDAL handles can give seg.faults]:
> 
> library(rgdal)
> logo <- system.file("pictures/Rlogo.jpg", package="rgdal")[1]
> x <- new("GDALReadOnlyDataset", logo)
> displayDataset(x)
> y <- getRasterData(x)
> z <- rowMeans(y, dims=2)
> dim(z)
> GDAL.close(x)
> 
> tif_driver <- new("GDALDriver", "GTiff")
> getDriverLongName(tif_driver)
> tif2 <- new("GDALTransientDataset", tif_driver, 77, 101, 1, 'Float64')
> bnd1 <- putRasterData(tif2, z)
> displayDataset(tif2)
> tif_file <- tempfile()
> saveDataset(tif2, tif_file)
> GDAL.close(tif2)
> GDAL.close(tif_driver)
> tif3 <- GDAL.open(tif_file)
> displayDataset(tif3)
> GDAL.close(tif3)
> 
> $ gdalinfo zlogo.tif
> Driver: GTiff/GeoTIFF
> Size is 101, 77
> Coordinate System is `'
> Corner Coordinates:
> Upper Left  (    0.0,    0.0)
> Lower Left  (    0.0,   77.0)
> Upper Right (  101.0,    0.0)
> Lower Right (  101.0,   77.0)
> Center      (   50.5,   38.5)
> Band 1 Block=101x10 Type=Float64, ColorInterp=Gray
> 
> (I was playing with filename zlogo.tif, it reads into GRASS OK, but 
> that's using the same GDAL drivers.)
> 
> Well, it works, though it's a bit too exciting dodging the seg.faults 
> coming from over-writing live object handles while experimenting. For 
> determined users, deleteDataset() works too (oh yes!). I'll try to wrap it 
> up to be a bit smoother. No world file yet, but I guess that could just be 
> copied? Suggestions welcome.
> 
> Roger
> 
> > 
> > > version
> >          _
> > platform i386-pc-mingw32
> > arch     i386
> > os       mingw32
> > system   i386, mingw32
> > status
> > major    2
> > minor    2.0
> > year     2005
> > month    10
> > day      06
> > svn rev  35749
> > language R
> > 
> > _______________________________________________
> > R-sig-Geo mailing list
> > R-sig-Geo at stat.math.ethz.ch
> > https://stat.ethz.ch/mailman/listinfo/r-sig-geo
> > 
> 
-- 
Timothy H. Keitt
Assistant Professor
http://www.keittlab.org/
http://www.utexas.edu/directory/index.php?q=Keitt