On 23/10/16 19:28, Eric Barnhill wrote: >> >>> Interesting! I think also looking at what is already existing in >> the commons library your contribution is clearly on the image processing >> side. Is that right? It's badly needed. I also would love to have it. >> Crucial point here is that this is in signal processing terminology >> a-causal so you essentially have all the data before you start processing >> it (= Fourier Transform, convolution). >> > Yes, I work with 3+D complex valued images so I am always extending code to > handle these cases. This is how I started contributing here. > > >> Looking at what is missing in the apache commons just now is: >> - IIR filters + design (my IIRJ) >> - 2D (image) filtering/convolution (your JVCL) >> - FIR filters (causal with delay line) + design (linear phase filters) >> > I agree this would be a great set of tools. > > Regarding image processing, a source that needs to be considered, to avoid > being redundant, is ImgLib2. ImgLib2 a great library (inherently ND and > generically typed) but I find the learning curve on ImgLib to be pretty > steep and the approach quite specialized. So the question for a possible > commons contribution is, is there room for a more "everyday" filtering > library fitting the commons mission, which benefits from being more readily > intuitive than ImgLib2? I think probably so. Certainly nothing out of line > with the more base components of commons-math. I'd say 2D/3D convolutions with any kernel size and taking care of boundary conditions are something which is pretty generic and should be as part of a math library. It can be used for image processing but also for other tasks. > > As an example in my case, I am interested in extending my image processing > filters to ND but I am not sure this makes sense for commons -- probably What do you mean with ND? > methods overloaded for 2D and 3D would suffice, and if I want to get > fancier I should develop within ImgLib. > > I'm not too crazy about proper FIR filters in JAVA because even in C++ they >> are just too slow and one would need to write them as JNI calls to C to >> make them run fast enough (for example a 50Hz notch for ECG at 1kHz >> requires 500taps at a bandwidth of 4Hz -- in theory!). Not sure how excited >> people here are about C/JNI calls. However the FIR filter _design_ = >> creating an impulse response is useful for a-causal offline computation >> using the convolution operation (but the 1D convolution is already >> implemented isn't it?). > > The commons math guidelines, which I assume for now extend to spin-off > projects, are here http://commons.apache.org/proper/commons-math/ . One > stipulation is no external dependencies beyond commons-math and the Java > SDK. This is one reason I have not tried to integrate my convolution > library which has JOCL and JTransforms dependencies. Well, that's the reason why I'm offering my IIR library because it has no other dependency than commons math. Actually the laguerre solver from commons math makes the Bessel filter design short and sweet. I guess somebody more senior here needs to comment on the dependencies. > > Though I should emphasize that I am a noob myself, I would suspect that > high-performance aspects of signal processing requiring native calls > probably don't suit commons terribly well and should perhaps be some sort > of extension library. That's certainly something I would be happy to work > on too. For example, maybe a base commons-filter library could be worked > out, which could be readily extensible with JNI, GPU, etc. I'd also say that in the 1st instance any low level calls should be avoided and then JNI can be added as an option. That's the reason why I like the IIR filter because it makes sense in JAVA and then if somebody wants to use it for audio then I could add the JNI implementation if there is demand.
I've spent the weekend adding maven support to the IIRJ library. So now a simple "mvn install" does the job. Also done the testing properly with "mvn test" which generates all the different kinds of impulse responses and puts them in different subdirs for evaluation. https://github.com/berndporr/iirj Best, /Bernd > > Eric > -- www: http://www.berndporr.me.uk/ http://www.linux-usb-daq.co.uk/ http://www.imdb.com/name/nm3293421/ Mobile: +44 (0)7840 340069 Work: +44 (0)141 330 5237 University of Glasgow School of Engineering Rankine Building, Oakfield Avenue, Glasgow, G12 8LT --------------------------------------------------------------------- To unsubscribe, e-mail: dev-unsubscr...@commons.apache.org For additional commands, e-mail: dev-h...@commons.apache.org
