Dear Ana,

Neither R nor geo, but the free program ImageJ is pretty good for this kind of image analysis.

http://rsb.info.nih.gov/ij/

Cheers,
David

On 1 Apr 2013, at 15:13, "A.P.B. Carneiro" <apbc2@cam.ac.uk<mailto:apbc2@cam.ac.uk>>
 wrote:

Dear all,

I am trying to calculate an area from a picture. I think I can use Spatial Analyst but I am not sure how to do it.

I have a picture from the wing of a bird, and from there, I want to calculate the area of a white patch. The picture is with a scale bar.

Is there a way to do that? There is not spatial information on the picture.

Thanks in advance,

Ana


On Sep 29 2012, r-sig-geo-request@r-project.org<mailto:r-sig-geo-request@r-project.org> wrote:

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Today's Topics:

 1. Re: plotting holes of esri shape files (Edzer Pebesma)
 2. Re: basic question about plotKML (Struve,Juliane)
 3. Re: basic question about plotKML (Edzer Pebesma)
 4. Re: basic question about plotKML (Struve,Juliane)
 5. Re: Create a raster brick from a netcdf using all levels
    (Robert J. Hijmans)
 6. Re: NaN / NA values in SpatialPixelDataFrame conversion
    (Robert J. Hijmans)
 7. Re: Error when trying to extract values for points in a
    SpatialPointsDataFrame (Robert J. Hijmans)


----------------------------------------------------------------------

Message: 1
Date: Fri, 28 Sep 2012 13:18:18 +0200
From: Edzer Pebesma <edzer.pebesma@uni-muenster.de>
To: "r-sig-geo@r-project.org" <r-sig-geo@r-project.org>
Subject: Re: [R-sig-Geo] plotting holes of esri shape files
Message-ID: <5065877A.5090805@uni-muenster.de>
Content-Type: text/plain; charset=ISO-8859-1

Stefan,

with the help of

http://www.stat.auckland.ac.nz/~paul/R/Paths/MurrellPaths.pdf

I corrected this in spplot. To run it, you'd need to compile from source
on svn, or source this in your R session:

https://r-forge.r-project.org/scm/viewvc.php/*checkout*/pkg/sp/R/spplot.R?root=rspatial

or wait for the next release on CRAN (due soon, I hope).

spplot now also supports holes in polygons when the polygons are the
main object to plot, contain holes, and something in the background
should shine through.

Building on the example in
https://stat.ethz.ch/pipermail/r-sig-geo/2012-September/016116.html

p1 = spplot(mask, col.regions='lightgrey',
  sp.layout = list("sp.grid", as(dem_ascii, "SpatialGridDataFrame"),
  col = bpy.colors(), first = TRUE), main = "spplot of mask")
p2 = spplot(dem_ascii, col.regions=bpy.colors(), main = "spplot of dem",
  sp.layout = list("sp.polygons", mask, fill = 'lightgray', first =
FALSE))
png('spplot.png', 600, 600)
print(p1, split = c(1,1,1,2), more = TRUE)
print(p2, split = c(1,2,1,2))
dev.off()

gives http://ifgi.uni-muenster.de/~epebe_01/spplot.png as output. Mind
the legends.

With best regards,

On 09/20/2012 10:32 AM, sluedtke wrote:
Dear friends, am trying to overlay a polygon data set as a SpatialPolygonDateFrame to
an existing plot. The data set has a hole in the middle, and I do not
want to have any filling in there. If a check the shape in a GIS,
everything looks fine, but using the following commands to do the plot,
the hole is filled. That is the code I am using, the data is attached. Thanks in advance!
Stefan
 ################################################################################################
library(sp)
library(rgdal)
library(raster)
library(latticeExtra)
 ############################################################################################### #read the DEM from the ASCII format
dem_ascii=raster(readGDAL("./zerafshan_mod_dem.asc"))
 ############################################################################################### # read additional data for printing mask=readOGR("./", "mask_zerafshan")
 ###############################################################################################
#plot this stuff
plot_dem=spplot(dem_ascii, col.regions=terrain.colors(400),
colorkey=list(width=1, space="right"))+
layer(sp.polygons(mask,fill="lightgray"))
print(plot_dem) ################################################################################################
mask_zerafshan.dbf (110 bytes) <http://r-sig-geo.2731867.n2.nabble.com/attachment/7580992/0/mask_zerafshan.dbf> mask_zerafshan.prj (143 bytes) <http://r-sig-geo.2731867.n2.nabble.com/attachment/7580992/1/mask_zerafshan.prj> mask_zerafshan.shp (173K) <http://r-sig-geo.2731867.n2.nabble.com/attachment/7580992/2/mask_zerafshan.shp> mask_zerafshan.shx (150 bytes) <http://r-sig-geo.2731867.n2.nabble.com/attachment/7580992/3/mask_zerafshan.shx> zerafshan_mod_dem.asc (1M) <http://r-sig-geo.2731867.n2.nabble.com/attachment/7580992/4/zerafshan_mod_dem.asc>
-- View this message in context: http://r-sig-geo.2731867.n2.nabble.com/plotting-holes-of-esri-shape-files-tp7580992.html Sent from the R-sig-geo mailing list archive at Nabble.com.
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--

PhD student
Evolutionary Ecology Group
Department of Zoology
University of Cambridge

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