From: Mulholland, Tom <Tom.Mulholland_at_dpi.wa.gov.au>

Date: Tue 22 Mar 2005 - 12:30:00 EST

R-help@stat.math.ethz.ch mailing list

https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html Received on Tue Mar 22 12:34:02 2005

Date: Tue 22 Mar 2005 - 12:30:00 EST

I've used rimage to read in graphics files (jpeg.) If I recall correctly, I think I had to install some libraries. What I can't recall is if it was any faster than pixmap, as I was mainly concerned with the file format and the forensic image processing possibilities.

Tom

*> -----Original Message-----
**> From: Ted.Harding@nessie.mcc.ac.uk
**> [mailto:Ted.Harding@nessie.mcc.ac.uk]
**> Sent: Monday, 21 March 2005 12:09 AM
*

> To: r-help@stat.math.ethz.ch

*> Subject: [R] Using locator() to digitise
**>
**>
**> Hi Folks,
**>
**> I'm contemplating using locator() to digitise external
**> graphics. To set context, I would be using X11 display
**> on Linux.
**>
**> To pre-empt the obvious comment: I've found on the R site
**> the suggestion to use the 'pixmap' package. I've tried
**> this, and it works; but it involves building a big R
**> object (the internal pixmap representation), and this
**> chokes my somewhat puny laptop (e.g. it can take about
**> 1 minute to draw the graphic inside a plot area using
**> addlogo(), with mucho swappo, and subsequently working
**> knee-deep in treacle). The following idea would be a lot
**> slicker.
**>
**> For examples: I have something like
**>
**> a) A scatterplot of data printed in a journal (but the
**> data values are not available;
**>
**> b) A contour map (on paper) of a region.
**>
**> So, I can scan the document, and obtain a file in some
**> graphics format (jpeg, pbm or png, say).
**>
**> Now: an idea which I find attractive is to be able to
**> overlay an R plot with axes onto a display of the graphics
**> file (produced as an X window by any suitable program such
**> as 'xv' or 'display') so that (if the overlay were possible)
**> clicking on the points of the graphic would in fact be
**> clicking on the R plot and, via locator(), generate the
**> R-plot coordinates of the mouse clicks which would correspond
**> to the selected points on the graphic.
**>
**> Provided the coordinate system of the R plot were properly
**> related to the graphic, the results would be a digitisation
**> of the selected points on the graphic.
**>
**> What seems to be needed for this idea to work is that
**> the R-plot should be displayed in an X11() device whose
**> background was completely transparent, so that when
**> moved over the (independently generated) display of the
**> graphic the latter would be visible (but locator() would
**> still be working on the R-plot itself). Window resizing
**> could look after the correspondence between graphic coordinates
**> and R-plot coordinates.
**>
**> The R plot itself could be empty (apart from coordinate axes)
**> or could contain "helper" elements such as grid lines, circles
**> (e.g. I want to digitise graphics points within a certain circle),
**> etc. "Helper" elements could be added to the R-plot by subsequent
**> 'lines' or 'points' commands (e.g. I identify two points on
**> the graphic, R-plot the line joining them, and then pick off
**> graphic-points which lie on the R-line).
**>
**> So this question is really about producing a "bare" R plot
**> on, as it were, a virtual acrylic transparency. It's certainly
**> possible to do such a thing in X: e.g. the cute "xteddy" is
**> in fact a picture of a bear on a completely transparent
**> rectangular background, though you'd never know by looking!
**>
**> Any comments?
**>
**> With thanks, and best wishes to all,
**> Ted.
**>
**>
**> --------------------------------------------------------------------
**> E-Mail: (Ted Harding) <Ted.Harding@nessie.mcc.ac.uk>
**> Fax-to-email: +44 (0)870 094 0861
**> Date: 20-Mar-05 Time: 16:09:11
**> ------------------------------ XFMail ------------------------------
**>
**> ______________________________________________
**> R-help@stat.math.ethz.ch mailing list
**> https://stat.ethz.ch/mailman/listinfo/r-help
**> PLEASE do read the posting guide!
**> http://www.R-project.org/posting-guide.html
*

>

R-help@stat.math.ethz.ch mailing list

https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html Received on Tue Mar 22 12:34:02 2005

*
This archive was generated by hypermail 2.1.8
: Fri 03 Mar 2006 - 03:30:52 EST
*