Gordon:
This is a copy of an off-list reply from May 2003, which may give some
assistance - not quite the same, because here the image was inserted into
an existing plot. It is based on using the pixmap package to import a
ppm or pnm file, then rescaling to fit the designated space.
Roger Bivand
---------- Forwarded message ----------
Date: Mon, 26 May 2003 11:26:21 +0200 (CEST)
From: Roger Bivand <[EMAIL PROTECTED]>
To: [EMAIL PROTECTED]
Cc:
Subject: Re: [R] overlapping a plot with an external image
> On Wednesday, May 21, 2003, at 04:38 PM, Prof Brian Ripley wrote:
>> On Wed, 21 May 2003, Meinhard Ploner wrote:
>
>>> It's possible to overlap an external image (jpg or pdf)
>>> with a plot generated with R?
>>
>>> Specifying the image as the background
>>> of the plot might not be possible...
>
>> Although this has been discussed, R graphics devices cannot as yet plot
>> bitmap images. So all one can do is to plot a set of rectangles: for
>> that the pixmap package might be helpful.
>
>> Although we might add the ability to plot a bitmap image, note that it
>> is not straightforward, as R screen graphics devices can be dynamically
>> resized. What should be done with a plotted image then? Interpolate
>> on the fly?
> The plotted image should be a logo of the project / department and I
> like to add it on every plot - for esthetical and descriptive reasons
Here is a very rough addlogo() using pixmap:
"addlogo" <- function(x, y, pixmap) {
if (is.list(x)) {
y <- x$y
x <- x$x
}
else if (missing(y))
stop("missing y")
if (!is.numeric(x) || !is.numeric(y))
stop("non-numeric coordinates")
if ((nx <- length(x)) <= 1 || nx != length(y) || nx > 2)
stop("invalid coordinate lengths")
[EMAIL PROTECTED] <- x[1]
[EMAIL PROTECTED] <- y[1]
[EMAIL PROTECTED] <- x[2]
[EMAIL PROTECTED] <- y[2]
[EMAIL PROTECTED] <- ([EMAIL PROTECTED] - [EMAIL PROTECTED]) / [EMAIL PROTECTED]
[EMAIL PROTECTED] <- ([EMAIL PROTECTED] - [EMAIL PROTECTED]) / [EMAIL PROTECTED]
plot(pixmap, add=TRUE)
invisible(pixmap)
}
which will work with locator() too. To maintain aspect, it shouldn't alter
the relative cell resolutions, and should just use the new x or y, bur
this is the general case. The handling of the location of the logo is
copied & pasted from legend().
Roger
--
Roger Bivand
Economic Geography Section, Department of Economics, Norwegian School of
Economics and Business Administration, Breiviksveien 40, N-5045 Bergen,
Norway. voice: +47 55 95 93 55; fax +47 55 95 93 93
e-mail: [EMAIL PROTECTED]
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