gpivtools (1)

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).

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_rot\90, gpiv_rot\180

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.

gpiv, gpiv_control

Gerber Van der Graaf