On Wed, 7 Feb 2018, Barry Rowlingson wrote:
I'd do this by saving the image on the graphics device as a PNG, then
creating a "world" file (with extension PNGW) from the coordinates of the
corners and the resolution of the PNG. This is a six line text file with
sufficient information to georeference a grid. That's enough for `gdal` to
understand it, and then the `gdal` utilities can convert it to a GeoTIFF
(or load into R using `raster` and then save as a GeoTIFF).
The tricky bit might be finding the corner coordinates of the graphics
device image. This is complicated by R leaving space for margins, or not
using your coordinate system.
Right - see the example in ASDAR 1st edition, chapter 4 chunks 42-44 in
http://www.asdar-book.org/data.php?chapter=3 (zero-based php)
which has par(mar=c(0,0,0,0), xaxs="i", yaxs="i") and widths and heights
from maptools::GE_SpatialGrid().
Roger
If this is a base graphics plot using the coordinate system units then you
can probably get them via some combination of the par() values, or you
might have set the margins to zero and that gives you the corners from
par()$usr (I think).
If its grid graphics (like spplot) then.... uhhh. someone else probably
knows how to do it.
Barry
On Wed, Feb 7, 2018 at 3:07 PM, Arnaud Mosnier <a.mosnier at gmail.com>
wrote:
Hi,
Long version:
I made a plot (a map) including SpatialPolygons representing the coast of
my region of interest, and a SpatialPointsDataframe representing
locations
of cities, and I want to save this map in GeoTiff format to allow other
people to use this map as a georeferenced background without having to
manage the various data sources. Is there a package/function in R that
would allow me to do that?
Note that converting the Spatial* objects to the raster format is not an
option because I want to be able to see the names of the cities on the
map.
In short:
Is there a way to save a plot composed of Spatial* elements in a GeoTiff
format?
Thanks
Arnaud
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