[Numpy-discussion] [ANN]: OpenPiv. A python package for PIV image analysis

Alex Liberzon alex.liberzon at gmail.com
Mon Apr 25 13:15:32 EDT 2011

Dear Fabrice, 

Let's take this discussion off-line, contact us directly through http://github.com/alexlib or to e-mail. It's a coincidence but I just finished wrapping the same library using SWIG :). Such a pity I didn't know about your work. I also believe that we talk about the same thing as I did it also to work with PIVMAT and was in touch with its author. We would be happy to use your stuff and include it as a part of OpenPIV. 

I'm not sure how much can we go into the 3D stuff (although my second big thing is managing the 3D-PTV http://ptv.origo.ethz.ch) and we do have tools for 3D analysis. I'd be very happy to release everything we have in our backyards, Matlab, C, Python, to bring it all together to a serious skikit or similar project based on Numpy/Scipy and Cython for the good of all fluid mechanics experimentalists. Such packages exist actually for the CFD data, I am not aware of the open source and free ones. 

Would you join our team? 

Best regards,
Alex Liberzon

Turbulence Structure Laboratory [http://www.eng.tau.ac.il/turbulencelab]
School of Mechanical Engineering
Tel Aviv University

Le dimanche 24 avril 2011 ? 16:53 +0200, Davide a ?crit :
> Hi all,
> I am pleased to announce the re-birth of OpenPiv, a python package for 
> the analysis of PIV images. PIV is a well established optical 
> measurement technique for fluid flows. The package has the goal of 
> provide an implementation of state-of-the-art processing algorithms, and 
> compete with commercial closed-source software packages.
> OpenPiv is in alpha state and several thing has to be done. However, the 
> code is already usable and a pure python implementation of the standard 
> cross-correlation algorithm is already available.
> OpenPiv needs developers and contributors, helping in with code and 
> documentation. If you can provide some, and if you are interested in 
> becoming a core developer, please drop us an email at openpiv-develop at 
> lists dot sourceforge dot net. A draft website can be found at 
> www.openpiv.net/python.
> Thanks for your attention,
> Davide Lasagna

Hi Davide
Investigations in fluid mechanics lead me to build a few months a
wrapper on the I/O functions from Davis (LaVision), a commercial
solution used to handle the complete procedure from camera calibration
to postprocessing velocity fields. 
I had to postprocess previous measurements stored in Davis format to a
deeper analysis than their software allows, so that I needed a tool able
to read data from their (almost documented) format.
The solution I found googling were not satisfying at the moment. For
example, PIVMAT [2] only worked for 2D fields and we were dealing with
3D flows and Stereoscopic PIV. After speaking with it author, it appears
that it would require too much work to support the third component in a
decent way.

The ctypes-based wrappers are available here
It is a quite dumb piece of code, but it allows to extract images or
velocity fields from binary files (extensions im7, imx and vc7),
avoiding some of the traps in the extraction of the data.

I would be happy if you consider useful this tool within OpenPIV. It
would also be possible to change the ctype dependance to cython...

Best regards

[1] http://www.lavision.de/en/products/davis.php
[2] http://www.fast.u-psud.fr/pivmat/
Fabrice Silva

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