Mailman 3 August 2013 - scikit-image

Re: skimage and opencv
by Emmanuelle Gouillart 22 Sep '16

22 Sep '16

Hi FranÃ¯Â¿Â½ois, that's an excellent question, and not a troll :-). Opencv is a very powerful library, but it focuses primarily on computer vision (feature detection and extraction, classification, ...), as opposed to image processing in general (with other tasks such as denoising, segmentation, ...). The other big difference is that skimage builds on numpy ndarrays, and uses the full power of the numpy API (including of course the basic facilities for processing arrays as images that come with numpy), as well as some of scipy functions (you could have added scipy.ndimage to your list -- a few functions in skimage are wrappers around scipy.ndimage, that exist for the sake of completeneness). One important consequence is that algorithms working for 3-d or even n-d images can be easily implemented in 3-d/n-d in skimage, whereas opencv is restricted to 2-D images (as far as I know). Thanks to the use of numpy arrays, the API of skimage is also quite pleasant for a numpy user, more than the API of opencv. A related difference is that skimage is written in python and cython, whereas opencv is a C++ library. The two libraries attract a different crowd of developers, and a Python/Cython toolkit based on numpy arrays is easier to develop and maintain inside the Scientific Python ecosystem. I'm sure that other devs/users will have things to add to this discussion! Cheers, Emmanuelle On Thu, Dec 27, 2012 at 02:06:08PM -0800, FranÃ¯Â¿Â½ois wrote: > Hi users and devs, > It came to my knowledge that another python library (based on C++ and C > codes) for image processing exists too : opencv > I understand that numpy intregrates some basic features and we need some > advanced features but I have the feeling that skimages is redoundant with > opencv in some ways. > What's the position of skimage about that? (Don't read this question as a > troll but like a real question). > I mean that similar features exist in both. Would not be possible to > reuse/integrate opencv or merge? what's the reason for keeping them apart? > My observation is there is 4 libraries to manipulate images: > * PIL > * numpy > * skimages > * opencv > That's a lot. > Cheers,

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Re: Contribution: circles and hough transform
by François 18 Jun '14

18 Jun '14

Hi, FYI, I plan to work on the detection of ellipses quite soon. Stefan indicated to me a reference which seems fairly simple to implement. Cheers, François.

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Get border pixels of labelled region
by Robin Wilson 12 Sep '13

12 Sep '13

Hi all, Is there a way to get the pixels on the border of a labelled region in an image using skimage? I've done edge detection, and then filled the resulting shapes (after some edge linking), and would now like to be able to get the pixels on the border of each of these shapes. I would have thought that getting borders would be an option in regionprops, but it doesn't seem to be. Any ideas? Cheers, Robin

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Sift on GPU
by Jérôme Kieffer 10 Sep '13

10 Sep '13

Dear Pythonistas, We are porting the SIFT keypoints extraction algorithm (available from IPOL) to GPU using PyOpenCL. For the moment, the keypoint location works and shows a speed-up of 5 to 10x (without tuning so far, vs C++). A lot of work is remaining, especially: * limit the memory footprint (700MB/10Mpix image currently) * calculate the descriptor for each descriptor * keypoint matching and image alignment. * best interleave of IO/CPU/GPU but we managed to port the most trickiest part to OpenCL (without using textures, which makes it running also on multi-core). I would like to thank the people who published their algorithm on IPOL; making unit testing possible. Last but not least, the code is open source and should have a BSD licence (even if there is a patent on the algorithm in the USA). https://github.com/pierrepaleo/sift_pyocl Cheers, -- Jérôme Kieffer <google(a)terre-adelie.org>

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Dividing a large image into smaller overlapping blocks for parallel processing
by Riaan van den Dool 01 Sep '13

01 Sep '13

Hi guys I would like to use scikit-image to process large images, for example (5696, 13500). In the interest of speed I need to divide the image into smaller sub-images with the possibility of processing these in parallel. If I define the sub-images so that neighbouring sub-images overlap then edge effects should not be a problem for the algorithm operating on each sub-image. This is probably a specific case of the more general border/edge-effect handling issue as addressed by the mode parameter here: http://docs.scipy.org/doc/scipy/reference/generated/scipy.ndimage.filters.c… My questions: 1. Is there already a image-division function/strategy implemented in scikit-image? 2. Is this something that might be included in future if an implementation is available? 3. Please share any references to articles or code that deals with this. Riaan

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HoG orientation
by angelatlarge 31 Aug '13

31 Aug '13

Just added a PR (#715<https://github.com/scikit-image/scikit-image/issues/715>) to allow computation of signed orientations in HoG. Minor feature, really, and perhaps not all that useful given that there is a substantial revision proposed to the HoG code in PR #703. All the PR proposes to do is to pull out the 180 degree constant into a separate variable and initialize it based on whether orientations should be signed or not.

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Difference between tutorials and longer examples
by François Boulogne 29 Aug '13

29 Aug '13

Hi, What's the difference between tutorials in the user guide http://scikit-image.org/docs/dev/user_guide/tutorials.html and longer examples in the gallery ? http://scikit-image.org/docs/dev/auto_examples/#longer-examples-and-demonst… Is there any reason to do not gather them? Cheers, -- François Boulogne. http://www.sciunto.org GPG fingerprint: 25F6 C971 4875 A6C1 EDD1 75C8 1AA7 216E 32D5 F22F

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Re: EuroSciPy sprint
by Marianne Corvellec 29 Aug '13

29 Aug '13

Congrats, guys! Sprinting is the best. :D On Wednesday, August 28, 2013 3:43:58 AM UTC-4, Juan Nunez-Iglesias wrote: > > Loved the sprint! I agree with Emmanuelle that it was way too short. I was > just hitting my stride when we left! If you know who's organising next > year's conference, I'd push them to have two days of sprinting. =) > > > On Wed, Aug 28, 2013 at 8:56 AM, Stéfan van der Walt <ste...(a)sun.ac.za<javascript:> > > wrote: > >> On Wed, Aug 28, 2013 at 8:46 AM, Emmanuelle Gouillart >> <emmanuelle...(a)nsup.org <javascript:>> wrote: >> > Would we publish such a blog post on your blog? If yes, how about I send >> > you a few elements about the Euroscipy sprint by e-mail? >> >> That'd be great, thanks! >> >> Stéfan >> >> -- >> You received this message because you are subscribed to the Google Groups >> "scikit-image" group. >> To unsubscribe from this group and stop receiving emails from it, send an >> email to scikit-image...(a)googlegroups.com <javascript:>. >> For more options, visit https://groups.google.com/groups/opt_out. >> > >

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Re: EuroSciPy sprint
by Juan Nunez-Iglesias 28 Aug '13

28 Aug '13

Loved the sprint! I agree with Emmanuelle that it was way too short. I was just hitting my stride when we left! If you know who's organising next year's conference, I'd push them to have two days of sprinting. =) On Wed, Aug 28, 2013 at 8:56 AM, Stéfan van der Walt <stefan(a)sun.ac.za>wrote: > On Wed, Aug 28, 2013 at 8:46 AM, Emmanuelle Gouillart > <emmanuelle.gouillart(a)nsup.org> wrote: > > Would we publish such a blog post on your blog? If yes, how about I send > > you a few elements about the Euroscipy sprint by e-mail? > > That'd be great, thanks! > > Stéfan > > -- > You received this message because you are subscribed to the Google Groups > "scikit-image" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to scikit-image+unsubscribe(a)googlegroups.com. > For more options, visit https://groups.google.com/groups/opt_out. >

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Re: EuroSciPy sprint
by Emmanuelle Gouillart 28 Aug '13

28 Aug '13

Hi StÃ¯Â¿Â½fan, yes, this sprint was a lot of fun! Although it's always too short! Would we publish such a blog post on your blog? If yes, how about I send you a few elements about the Euroscipy sprint by e-mail? Cheers, Emmanuelle On Wed, Aug 28, 2013 at 01:09:09AM +0200, StÃ¯Â¿Â½fan van der Walt wrote: > Hi everyone, > I want to send a big shout-out to everyone who sprinted on skimage at > EuroSciPy2013! You guys did a great job, and it was a lot of fun watching all > the pull requests and comments fly by. > Emmanuelle, how about we do a short blog post on the event? I can combine it > with the results of the US sprint that I still have on the shelf. > StÃ¯Â¿Â½fan

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