Gpiv

Gpiv is a graphic user interface program for recording and analyzing images obtained from a fluid flow that has been seeded with tracer particles by the so-called Particle Image Velocimetry technique (PIV).

The program allows to have a quick overview of the parameter settings of all processes, easily changing them, executing the processes and visualizing their results in an interactive way . Gpiv has been built with the Gtk/Gnome libraries and includes many interesting features.

Features:General
- Data storage in ASCII or HDF format.
- Integration within the Gnome desktop: Loading of images with "drag and drop" from the gnome file-manager Nautilus into the buffer list. Inclusion of Gpiv launcher into menu and taskbar (pre-compiled package).
- Pipeline execution of enabled processes.
- Batch processing on selected buffers.
- Minimizing the console interface when desired by undisplaying the parameter settings tabulator and detaching the buffer list.
- Quick execution by means of toolbar buttons.
- On-line help from info line, tooltips and manual.
Display
- Visualization of the image(pair).
- Shows interrogation area contours that will be highlighted when pointing to them.
- Displaying of pointer position and belonging estimated values.
- In and out zooming of displayed features.
- Defining vector length.
- Showing of vector colors related to specified criterium (validation threshold, correlation peak number, enabled/disabled)
- Displaying of derived scalar quantities (vorticity and strain) as background.
Record
- Triggering of lasers and camera by means of RTAI over the parallel port of the Computer.
- Recording images from a IIDC-compliant (CCD) camera that is connected to the Computer by the IEEE1394 (Firewire, I-Link) protocol.
Image
- Displaying image name, dimensions and type of correlation (cross or auto).
- Defining of spatial and time scales, position of image within the experiment.
- Adding and updating header information (date of creation, project, comment etc).
Interrogation
- Interrogation by means of image-deformation techniques, using 5th order B-spline interpolation.
- Adaptive interrogation area sizes.
- Grid refinement by using bi-linear interpolation with shifted knots.
- Validation after each iterative interrogation step.
- Global pre-shifting.
- Local pre-shifting or zero offsetting of the interrogation areas with forward or central difference scheme at integer number of pixels.
- Three interpolation schemes for sub-pixel estimation.
- Cross and auto correlation.
- Choice of correlation peak for estimating particle displacements.
- Arbitrary interrogation area dimensions.
- Interrogation at the entire image or at an Area Of Interest, resulting into a displacement field on a rectangular grid.
- Interrogation at a single arbitrary point, along a vertical or horizontal line by pointing in the image frame.
- Re-interrogation of a single area with different parameters.
- Dragging a single interrogation area from the rectangular grid.
- Visualization of interrogation area's and correlation function.
Data validation
- Enabling and disabling of PIV estimators manually.
- Graphical representation of histogram containing displacements at sub-pixel level to check on peak-locking effects.
- Graphical representation of histogram of residuals, calculation of threshold for acceptance of PIV estimators.
- Validation on outliers by SNR value or median test from normalized residus.
Post-processing
- Time and spatial scaling.
- Calculation of statistics and subtraction of the mean value from the estimators.
- Calculation of vorticity and strain.