On Thu, 9 Mar 2006, Christian Jost wrote: > Dear all, > > I try to figure out how to use R to count the number of pixels of the > same color in some gray-level picture. I managed to read it in either > tiff or jpeg format, but the returned pixmap object keeps its > information out of (my) reach. Is there an easy way to tabulate the > different color/graylevel pixels and their numbers? Or should I use a > completely different (free) software?
The objects are new-style class objects, so they are documented internally - query by getSlots() or from ?"pixmap-class": library(pixmap) x <- read.pnm(system.file("pictures/logo.ppm", package="pixmap")[1]) z <- as(x, "pixmapGrey") class(z) getSlots(class(z)) # lets you know what the slots are greydata <- slot(z, "grey") # extract the slot object summary(c(greydata)) # c() to flatten a matrix length(unique(c(greydata))) length((c(greydata))) # rather a lot of different values, let's round: rgreydata <- round(greydata*10) length(unique(c(rgreydata))) # looks good table(c(rgreydata)) I assume that you converted from tiff or jpeg to pnm outside pixmap. > > Thanks for any hint, Christian. > -- Roger Bivand Economic Geography Section, Department of Economics, Norwegian School of Economics and Business Administration, Helleveien 30, N-5045 Bergen, Norway. voice: +47 55 95 93 55; fax +47 55 95 95 43 e-mail: [EMAIL PROTECTED] ______________________________________________ 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