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: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] > Sent: Monday, 21 March 2005 12:09 AM > To: [email protected] > 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) <[EMAIL PROTECTED]> > Fax-to-email: +44 (0)870 094 0861 > Date: 20-Mar-05 Time: 16:09:11 > ------------------------------ XFMail ------------------------------ > > ______________________________________________ > [email protected] mailing list > https://stat.ethz.ch/mailman/listinfo/r-help > PLEASE do read the posting guide! > http://www.R-project.org/posting-guide.html > ______________________________________________ [email protected] mailing list https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html
