[R] embed image (png) in postscript (device)

[Prof Brian Ripley]

On Fri, 1 Sep 2006, Hans-Peter wrote:

> Hi,
> 
> I output multiple "grid-package-based" plots to the postscript device.
> Because the graphics are complicated and consists of a lot of datapoints
> (~200'000) the files become really big. To avoid this big files and to
> shorten the creation, I currently print the plots to the png device and
> manually combine them into one multipaged pdf document.
> 
> My question is, it is possible to do this in R directly?
> Probably I would have to create a png plot first, then reimport it into R
> and "put" it on the ps device. Is this a realistic way (in principle) ?
> 
> If there is no package to read png files (I didn't find anything), I
> probably could solve this. 

There are various ways to do so: one is to convert to a format pixmap 
knows, another to convert to TIFF and use rtiff.

> But I still don't know if it would be possible to
> "put" this memory representation to a ps device.

Only crudely.  There is nothing in the R graphics model related to 
bitmaps.  What you could do is draw each pixel as a rectangle (as image() 
does), but then your file size will be even bigger and the chances of it 
being rendered accurately are not high.

-- 
Brian D. Ripley,                  ripley at stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
1 South Parks Road,                     +44 1865 272866 (PA)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595