Welcome to libim7’s documentation!¶

Build and install¶

For non-Windows OSes, the build of the extension is handled by the DistUtils mechanisms:

$ cd libim7
$ ls
libim7.py  SConstruct  License.txt  setup.cfg  setup.py  src  test
$ python setup.py build
$ ls
build  libim7.py  SConstruct  License.txt  setup.cfg  setup.py  src  test  _im7.so

The file named _im7.so (or _im7.dynlib on Mac OSes?) contained the Python extension for the code provided by LaVision.

On Windows, one has first to build a shared library file (call it _im7.dll) linked against the zlib. The SConstruct file is provided and automates this step using the sources in the folder src/:

C:\path\to\libim7\>scons
C:\path\to\libim7\>python setup.py build

For Python to be able to find the module, you need to set the path (using sys.path() ) or install the library:

# python setup.py install

Usage¶

Once build, you can import the module named libim7. The entry point is the function :function:`libim7.readim7` that retrieves the Buffer and the AttributeList objects from a given file.

>>> import libim7
>>> buf, att = libim7.readim7('myfile.im7')

All information accessible from LaVision Software is shown in the AttributeList

>>> print(att)

For an image file, you can get the number of frames and these various frames

>>> print "Number of frames:",buf.nf
>>> buf.get_frame(0)

For velocity field files (for example from LaVision Davis), the various components of the velocity field are retrieved and can be manipulated like numpy.ndarray() with:

>>> buf.x
>>> import matplotlib.pyplot as plt
>>> plt.imshow(buf.vx, extent=[buf.x[0], buf.x[-1], buf.y[0], buf.y[-1]])
>>> plt.figtitle(r"$v_x$ (%s)" % buf.scaleI.unit)
>>> plt.show()

Reference API¶

This project intends to provide a simple pythonic interface to read Particle Image Velocimetry (PIV) image and vector fields files created by LaVision Davis software. It bases on ctypes to build an object-oriented interface to their C library.

libim7.readim7(filename, scale_warn=False)¶

Read the file created by LaVision software and returns the related Buffer and AttributeList objects.

Returns :	buf : libim7.Buffer att : libim7.AttributeList

class libim7.Buffer¶

An object containing either the various frames of an Image file, or the various components of a field (probably the velocity field).

Attributes

class libim7.AttributeList¶

Methods

as_dict
delete
get_pairs

libim7.save_as_pivmat(filename, buf, att=None)¶

Save single file data according to PIVMAT format http://www.fast.u-psud.fr/pivmat/html/pivmat_data.html