NAME
gpivtools - The PIV tool suite.
DESCRIPTION
gpivtools is a set of command-line driven programs for the so-called
Digital Particle Image Velocimetry (DPIV). It contains programs for
image recording, processing and analysing (resulting into estimators of
particle displacement, i.e. PIV data), PIV data validation programs and
post-processing tools for manipulating and calculating (scalar)
derivatives of the PIV data.
Though the command-line driven tools are mainly intended for non-
interactive processing, its outputs may directly be visualized in a
graphical way with the aid of gnuplot.
The parameters and options to be used for most of the gpivtools are
provided by Libgpiv. They are subsequently searched in ./gpivrc at
local directory, at $HOME/.gpivrc (hidden) or at the system-wide
configuration file gpiv.conf, which is mostly found at /etc for UNIX-
like operating systems. Each parameter is described by the process key:
GENPAR (general parameters), CAM (camera settings), TRIG (trigger
settings), IMG (image header), IMGPROC (image processing), PIV (piv
interrogation), VALID (piv data validation) or POST (piv post
processing) and the parameter name, separated by a dot (.), followed by
its value. Some of the parameters are optional. The parameters may be
defined in arbitrary order. Blank lines and comment (starting with a
pound sign (#) at the first column) may be included in the parameter
files. The parameters may be overruled by the command line options of
each tool. Libgpiv provides default parameter values if they are not
defined in one of the configuration files or by an option key at the
command line.
In case stdin and stdout is used, verbose output of the programs is
suppressed in order to avoid contamination of the output data. If
filename is used for overruling stdin and stdout, the parameters are
written to filename.par. By renaming this file to ./gpivrc or
$HOME/.gpivrc, the parameters may directly be re-used for identic
processing of other images and PIV data. The parameters defined in
$HOME/.gpivrc and in /etc/gpiv.conf are also used by the Graphic User
Interface program gpiv.
The programs understand different image formats: Portable Network
Graphics (filename.png), HDF5 (filename.hdf), raw binary data
(filename.r) that is accompanied by an ASCII header file (filename.h),
and LaVision’s (tm) uncompressed image format (filename.img). Other
formats that use lossless compression (TIF, GIF, PGM, BMP) are
converted to PNG on the fly. For interrogation of double-framed images
using cross-correlation, the second image has to be concatenated after
the first one, if this has not already been done by the recording
camera. This might be performed by gpiv_combing. Image parameters are
read from the header or from the configuration resources (containing
the IMG key).
GPIV-TOOLS COMMANDS
Here is the complete list of available gpivtools programs. See their
individual man pages for a more extended description.
gpiv_aint
Calculates mean image intensity at each interrogation area.
This program uses the IMG, PIV and POST parameters.
gpiv_combing
Combines two images into one image file for cross-correlation.
This program uses the IMG parameters.
gpiv_errvec
Searches the erroneous vectors in a PIV data file and eventually
substitutes them with new values. This program uses the PIV and
POST parameters.
gpiv_fi-keyline
Filters each line that starts with a keyword. This program does
not use the parameter resources from Libgpiv.
gpiv_hdf2piv
Converts hdf5 PIV data (extension .hdf) to ASCII data. This
program does not use the parameter resources from Libgpiv.
gpiv_imgproc, gpiv_mktestimg, gpiv_smooth, gpiv_hilo, gpiv_clip,
gpiv_fft, gpiv_invfft, gpiv_lowpass, gpiv_highpass, gpiv_getbit,
gpiv_mktestimg
(PIV) image processing programs. These programs use the IMGPROC
parameters.
gpiv_img2gpiv
Depreciated: use gpiv_combing instead. Converts images into raw
data (extension .r) format with the belonging ASCII header
(extension .h) or into hdf format (with extension .hdf). This
program does not use the parameter resources from Libgpiv.
gpiv_manipiv, gpiv_fasty, gpiv_flipx, gpiv_flipy, gpiv_revert,
gpiv_rot90, gpiv_rot180
Simple data manipulation tool for PIV data. These programs use
the POST parameters.
gpiv_peaklck
Tests PIV data on the so-called peak-locking effect by
printing/displaying an histogram of the particle displacements
at sub-pixel level. This program uses the VALID parameters.
gpiv_piv2gnuplt
Converts PIV data gnuplot data. Besides this, image
interrogation and post-processing programs are able to display
their results directly (mostly with the -g option). This program
does not use the parameter resources from Libgpiv.
gpiv_piv2grid
Converts PIV data to grid data for generating contour plots with
Plotmtv. This program does not use the parameter resources from
Libgpiv.
gpiv_piv2hdf
Converts ASCII PIV data to hdf5 formatted data (extension .hdf).
This program does not use the parameter resources from Libgpiv.
gpiv_piv2vec
Adds header to PIV data for a vector plot with Plotmtv. This
program does not use the parameter resources from Libgpiv.
gpiv_process-chain
Processes a pipeline of Gpiv-tool command’s, forming process a
chain from image recording, image processing, image
interrogation, data validation, data post-processing. This
program does not use the parameter resources from Libgpiv.
gpiv_recimg
captures images from a IIDC-compliant CCD camera with IEE1394
connection. This program uses the IMG parameters.
gpiv_rr
Interrogates images in order to obtain displacement estimators
of particles for (Digital) Particle Image Velocimetry. This
program uses the PIV and VALID parameters.
gpiv_sca2gri
Converts scalar data from gpiv to grid data for contour plotting
with Plotmtv This program does not use the parameter resources
from Libgpiv.
gpiv_scale
Spatial and time scaling program for PIV data. This program
uses the IMG and POST parameters.
gpiv_series
Script for (parallel) processing a series of numbered files.
This program does not use the parameter resources from Libgpiv.
gpiv_suta
Subtracts time-avaraged velocities (local mean) from the PIV
estimators. This program does not use the parameter resources
from Libgpiv.
gpiv_s-avg
Spatial statistics of PIV data. This program uses the POST
parameters.
gpiv_t-avg
Calculates time-avaraged mean and rms from a series of PIV data.
This program does not use the parameter resources from Libgpiv.
gpiv_t-avg-img
Calculates time-averaged values from a series of images at each
pixel. This program uses the GENPAR parameters.
gpiv_t-corr
Calculates the velocity correlation as function of time
(Eulerian correlation) from a series PIV data sets This program
does not use the parameter resources from Libgpiv.
gpiv_trig
Triggers a (double Nd_YAGG) laser on a CCD camera. This program
uses the TRIG parameters.
gpiv_uhisto
Tests PIV data by printing/displaying an histogram of the
horizontal particle displacements. This program uses the VALID
parameters.
gpiv_vhisto
Tests PIV data by printing/displaying an histogram of the
vertical particle displacements. This program uses the VALID
parameters.
gpiv_vorstra, gpiv_vorty, gpiv_nstrain, gpiv_sstrain
Calculates the differential quantities vorticity, shear strain
and normal strain from PIV data. These programs use the POST
parameters.
SEE ALSO
gpiv, gpiv_control
AUTHOR
Gerber Van der Graaf
26 March 2008