Hi All, I really like to thank you for the answers, while I was searching for some edge detection and clustering algorithms, Moshe came with a simple but effective solution: use the area to find the diameter!
But I tried Moshe's solution, but I couldn't figure out what you mean with morphological closing and the labeling to split the images. Could you please clarify this a bit? Thanks for your support Bart Moshe Olshansky-2 wrote: > > Hi Bart, > > One more comment: > > You do not really need the morphological closing to > close the "holes" inside the circles. Another > possibility is to reverse the black-and-withe picture, > i.e. make the holes and background be 1 and the > circles 0, label the connected components and then > only the component which touches the boundaries is the > background while all other components are "holes" and > you can make them white (1) in the original > black-and-white image. > > --- Moshe Olshansky <[EMAIL PROTECTED]> wrote: > >> Hi Bart, >> >> I have never used image processing software in R (I >> was doing this with Matlab), but here is what I >> would >> have done algorithmically: >> 1) convert the picture to gray-scale >> 2) find a threshold value which separates the >> circles >> from the background and convert your image to black >> and white >> 3) if the circles are far apart use morphological >> closing to fill in small holes inside the circles >> (may >> be do this several times) >> 4) use labeling to split the image into connected >> components >> 5) for each connected component get it's area (the >> number of pixels) and use the formula S = Pi*R^2 to >> find the approximate radii. >> >> Regards, >> >> Moshe. >> >> --- Julian Burgos <[EMAIL PROTECTED]> wrote: >> >> > Hi Bart, >> > >> > If you only have 36 circles, the fastest way would >> > be to use some image >> > processing software and measure the circles "by >> > hand". One option is to >> > use ImageJ, which you can download here >> > >> > http://rsb.info.nih.gov/ij/ >> > >> > Julian >> > >> > Bart Joosen wrote: >> > > Hi, >> > > >> > > Maybe this is more a programming questions than >> a >> > specific R-project question, but maybe there is >> > someone who can point me in the right direction. >> > > >> > > I have a picture of cirkels which I took with a >> > digital camera. >> > > Now I want to use the diameter of the cirkels on >> > the picture for analysis in R. >> > > I can use pixmap to import the picture, but how >> do >> > I find the outside cirkels and calculate the >> > diameter? >> > > I pointed out that I can use the edci package, >> but >> > then I need to preprocess the data to reduce the >> > points, otherwise it takes a long time, and my >> > computer crashes. >> > > >> > > If you want to see such a picture, I cropped a >> > larger one, and highlighted the cirkel which is of >> > interest. >> > > In a real world, this is a plate with 36 >> cirkels, >> > which all should be measured. >> > > www.users.skynet.be/fa244930/fotos/outlined.jpg >> > > >> > > >> > > Thanks for your time >> > > >> > > Bart >> > > [[alternative HTML version deleted]] >> > > >> > > ______________________________________________ >> > > 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 >> > > and provide commented, minimal, self-contained, >> > reproducible code. >> > > >> > > >> > >> > ______________________________________________ >> > 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 >> > and provide commented, minimal, self-contained, >> > reproducible code. >> > >> >> ______________________________________________ >> 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 >> and provide commented, minimal, self-contained, >> reproducible code. >> > > ______________________________________________ > 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 > and provide commented, minimal, self-contained, reproducible code. > > -- View this message in context: http://www.nabble.com/Calculating-diameters-of-cirkels-in-a-picture.-tf4319669.html#a12343143 Sent from the R help mailing list archive at Nabble.com. ______________________________________________ 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 and provide commented, minimal, self-contained, reproducible code.
