Re: [Rd] invalid graphics state using dev.print (fwd)

From: Prof Brian Ripley <ripley_at_stats.ox.ac.uk>
Date: Mon 20 Feb 2006 - 07:56:57 GMT

On Mon, 20 Feb 2006, Paul Murrell wrote:

[...]

>> >> x11()
>> >> plot(rnorm(10))
>> >> dev.print(png)

>> Paul> Error in dev.copy(device = function (filename = "Rplot%03d.png", width =
>> Paul> 480, :
>> Paul> invalid graphics state

> I think the problem is that the width and height of the PNG device is
> being taken (without regard for units) from the X11 device. So
> approximately 7 inches square screen window gets drawn into
> approximately 7 *pixel* square PNG file and (understandably) R complains
> that there is not enough room for the plot.

Yes, that it how it is documented to work.

> Another workaround is something like ...
>
> dev.print(png, width=480, height=480)

(Just one will do if you want to preserve the aspect ratio.)

> ... and a fix requires making dev.print() smarter so that it figures out
> that it needs to convert width/height from inches to pixels.

I don't think there is a way to do that unambiguously (there is no standard way to do the conversion), and in any case dev.print() was passed a function, not the name of a function, and so does not in general know how it behaves (and your 'png' need not be R's png()).

All we can do is to re-emphasize this on the help page, and add a warning if a known bitmap device is detected (possibly inaccurately) by name.

BTW, I think it was perverse to call dev.print() except to do printing.

-- 
Brian D. Ripley,                  ripley@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

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Received on Mon Feb 20 18:59:00 2006

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