问题
Where can I find a free, very quick, and reliable implementation of FFT in C#?
That can be used in a product? Or are there any restrictions?
回答1:
AForge.net is a free (open-source) library with Fast Fourier Transform support. (See Sources/Imaging/ComplexImage.cs for usage, Sources/Math/FourierTransform.cs for implemenation)
回答2:
The guy that did AForge did a fairly good job but it's not commercial quality. It's great to learn from but you can tell he was learning too so he has some pretty serious mistakes like assuming the size of an image instead of using the correct bits per pixel.
I'm not knocking the guy, I respect the heck out of him for learning all that and show us how to do it. I think he's a Ph.D now or at least he's about to be so he's really smart it's just not a commercially usable library.
The Math.Net library has its own weirdness when working with Fourier transforms and complex images/numbers. Like, if I'm not mistaken, it outputs the Fourier transform in human viewable format which is nice for humans if you want to look at a picture of the transform but it's not so good when you are expecting the data to be in a certain format (the normal format). I could be mistaken about that but I just remember there was some weirdness so I actually went to the original code they used for the Fourier stuff and it worked much better. (ExocortexDSP v1.2 http://www.exocortex.org/dsp/)
Math.net also had some other funkyness I didn't like when dealing with the data from the FFT, I can't remember what it was I just know it was much easier to get what I wanted out of the ExoCortex DSP library. I'm not a mathematician or engineer though; to those guys it might make perfect sense.
So! I use the FFT code yanked from ExoCortex, which Math.Net is based on, without anything else and it works great.
And finally, I know it's not C#, but I've started looking at using FFTW (http://www.fftw.org/). And this guy already made a C# wrapper so I was going to check it out but haven't actually used it yet. (http://www.sdss.jhu.edu/~tamas/bytes/fftwcsharp.html)
OH! I don't know if you are doing this for school or work but either way there is a GREAT free lecture series given by a Stanford professor on iTunes University.
https://podcasts.apple.com/us/podcast/the-fourier-transforms-and-its-applications/id384232849
回答3:
Math.NET's Iridium library provides a fast, regularly updated collection of math-related functions, including the FFT. It's licensed under the LGPL so you are free to use it in commercial products.
回答4:
I see this is an old thread, but for what it's worth, I have a free (MIT License) 1-D power-of-2-length-only C# FFT implementation here: http://gerrybeauregard.wordpress.com/2011/04/01/an-fft-in-c/
I haven't compared its performance to other C# FFT implementations. I wrote it mainly to compare the performance of Flash/ActionScript and Silverlight/C#. The latter is much faster, at least for number crunching.
回答5:
http://www.exocortex.org/dsp/ is an open-source C# mathematics library with FFT algorithms.
回答6:
Here's another; a C# port of the Ooura FFT. It's reasonably fast. The package also includes overlap/add convolution and some other DSP stuff, under the MIT license.
https://github.com/hughpyle/inguz-DSPUtil/blob/master/Fourier.cs
回答7:
An old question but it still shows up in Google results...
A very un-restrictive MIT Licensed C# / .NET library can be found at,
https://www.codeproject.com/articles/1107480/dsplib-fft-dft-fourier-transform-library-for-net
This library is fast as it parallel threads on multiple cores and is very complete and ready to use.
回答8:
The Numerical Recipes website (http://www.nr.com/) has an FFT if you don't mind typing it in. I am working on a project converting a Labview program to C# 2008, .NET 3.5 to acquire data and then look at the frequency spectrum. Unfortunately the Math.Net uses the latest .NET framework, so I couldn't use that FFT. I tried the Exocortex one - it worked but the results to match the Labview results and I don't know enough FFT theory to know what is causing the problem. So I tried the FFT on the numerical recipes website and it worked! I was also able to program the Labview low sidelobe window (and had to introduce a scaling factor).
You can read the chapter of the Numerical Recipes book as a guest on thier site, but the book is so useful that I highly recomend purchasing it. Even if you do end up using the Math.NET FFT.
回答9:
For a multi-threaded implementation tuned for Intel processors I'd check out Intel's MKL library. It's not free, but it's afforable (less than $100) and blazing fast - but you'd need to call it's C dll's via P/Invokes. The Exocortex project stopped development 6 years ago, so I'd be careful using it if this is an important project.
来源：https://stackoverflow.com/questions/170394/an-implementation-of-the-fast-fourier-transform-fft-in-c-sharp