---
name: "gpiv_lowpass"
section: "1"
platform: "linux"
package: "gpivtools"
version: "0.3.3-1"
release: "Debian 4.0 (Etch)"
platforms: ["linux"]
url: "https://new.carta.tech/gpiv_lowpass"
---

# gpiv\_lowpass(1)

Image processing program for PIV images.

## NAME

gpiv\_imgproc gpiv\_smooth gpiv\_hilo gpiv\_clip gpiv\_fft gpiv\_invfft gpiv\_lowpass gpiv\_highpass gpiv\_getbit - Image processing program for PIV images.

## SYNOPSIS

**gpiv\_imgproc** \[**-b** *N*\]  \[**-c** *int*\]  \[**-f** *filename*\]  \[**--filter** *N*\]  \[**-h** \| **--help**\]  \[**-p** \| **--print**\]  \[**-o** *N* \| **--operation** *N*\]  \[**-r** *int*\]  \[**-t** *N* \| **--threshold** *N*\]  \[**-w** *N*\]  \[**-v** \| **--version**\]  \< *stdin* \> *stdout*

## DESCRIPTION

**gpiv\_imgproc** *Processes, filters or converts images in order to* *improve the interrogation for Particle Image Velocimetry.* *smooth*: smoothing filter, *hilo* : high-low filter, *clip*: clipping *fft* : Fast Fourier Transform, *invfft*: Inverse  Fast Fourier Transform, *lowpass*: low-pass filtering, *highpass*: high-pass filtering *getbit*: get bit bumber. *mktestimg*: generates test image-pair for PIV

The parameters read from the configuration resources (containing the key **GPIV\_IMGPROC**) may be overruled by the command line options, as explained below.

## Options

- **-b** *N*

  **In case of using getbit** *N* denotes the bit number \[0, .., 7\]

  **-c** *N*  Specify the number of columns with *N* that contains the image.

- **-f** *filename*

  Overrides stdin and stdout with *filename*. The *filename* has to be given without its **.r** extension. The output will be written to *filename***..proc.r**. Parameters are stored  in *filename***.par** and may be used for future use by including them  in *./gpivrc*.

- **--filter** *N*

  Only if **gpiv\_imgproc** is used. image filter to be performed: make test image (*N*=0), smoothing (*N*=1), high-low filtering (*N*=2), clipping (*N*=3), fft (*N*=4), inverse fft (*N*=5), lowpass filter (*N*=8), highpass filter (*N*=9), getbit (*N*=10).

- **-h** \| **--help**

  On-line help

- **-o** *N* \| **--operation** *N*

  In case of using **smoothing**: set pixel equal to the mean of the window value (*N*0), subtract mean from from pixel (*N*1) add (*N*2), multiply (*N*3) or divide (*N*4)

- **-r** *N*

  Number of rows *N* that contains the image.

- **-t** *N* \| **--threshold** *N*

  In case of using **clip**: threshold value to be set to zero

- **-v** \| **--version**

  Print version information on standard output, then exit successfully.

- **-w** *N*

  window size (default: 15)

- gpivtools

  ## SEE ALSO

## AUTHOR

Gerber Van der Graaf