Antw: Re: import a jpg/etc. map into R?

Marcelino de la Cruz  13.09.11 12.47 Uhr >>>

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Dear all,

The answer may well be 'no', but does anyone 
know of a straightforward way to import into R a 
map in the form of a simple jpeg (or bmp, gif, etc.) image file?

I'm thinking of a situation where you have something like this:

http://www.learnnc.org/lp/media/uploads/2007/09/1492spain.jpg

or

http://www.spainthenandnow.com/userimages/Spain%20General%20Map%20Wikimedia.png

Latitude and longitude lines are given in the 
image, and they should be usable for identifying 
the geographical location of any given pixel, 
but the projection of the map is not immediately 
apparent, and the map is not in a vector format 
where lines or polygons can be easily 
identified. What I'd like to do is read in this 
kind of file, have R find the edges (identified 
somehow by differences in pixel colours I 
guess), and convert the areas defined by those 
edges into a SpatialPolygons object, with lat/long coordinates.

There may well be no easy way to do this (or not 
even a difficult way), but I thought I'd check 
if anyone has any ideas. I prefer to use R, but 
if some other (preferably open source) software 
could help me, I'd be interested to know. Even 
suggestions like "IF you could get it into X 
format, THEN you could*" might be useful. I'm 
not a GIS person, unfortunately. On the other 
hand, I am pretty handy with R, and a regular 
user of several of the maps/spatial/raster packages.

Any help would be much appreciated.

- Malcolm


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