[R] import a bitmap image and add it to graphics display
Roger.Bivand at nhh.no
Fri Aug 6 17:54:53 CEST 2004
On Thu, 5 Aug 2004, Wolfram Fischer wrote:
> > Hello
> > Is there a possibility to import and add a bitmap image (png or
> > similar) to a R graphics display. It would be helpful e.g. to
> > locate positions of points of a scanned map or to add a background
> > to a R graphic.
> > Wolfram
> I found the package pixmap with the functions
> x <- read.pnm( file )
> This plots pnm pictures as R graphics.
> (Other picture formats can be converted to pnm pictures
> by several pnm commands on Linux or by using gimp.)
> Overlaying such a picture with a graph could be done as follows:
> m <- 20 ; points( x=m*c(0,1,2), y=m*c(0,2,1), col='red', type='b', lwd=5 )
> There rests a problem with the scale:
> Question: How can I scale a pixmap object?
This is covered in the code for the addlogo function in the pixmap
> getMethod("addlogo", "pixmap")
which uses the pixmap bounding box and user-supplied coordinates and an
aspect argument to scale a pixmap object. If the function itself doesn't
do what you need, it does show the slots you could use directly.
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