2.11.13 fft_filter2

Contents

Menu Information

Analysis: Signal Processing: 2D FFT Filters

Brief Information

Perform 2D FFT filtering

Additional Information

Minimum Origin Version Required: 8.5Pro SR0

Command Line Usage

fft_filter2 filter:=high window:=ideal type:=hertz cutoff:=50 ;

X-Function Execution Options

Please refer to the page for additional option switches when accessing the x-function from script

Variables

Display
Name 		Variable
Name 		I/O
and
Type 		Default
Value 		Description
Input Matrix im

Input

MatrixObject

<active>
 Specify the input matrix. The matrix should be numeric. Thus, images should be converted into data before 2D FFT Filters analysis is applied.
Filter Type filter

Input

int

0
 Specify the filter type.

Option list:

  • low:Low Pass
    Low-pass filter that removes the frequencies above the cut-off frequency while keeping other frequencies unaltered.
  • high:High Pass
    High-pass filter that removes the frequencies below the cut-off frequency while keeping other frequencies unaltered.
  • bandpass:Band Pass
    Band-pass filter that removes the frequencies that are below the lower cutoff frequency or above the upper cutoff frequency while keeping other frequencies unaltered.
  • bandblock:Band Block
    Band-block filter that removes the frequencies that are between the lower cutoff frequency and the upper cutoff frequency while keeping other frequencies unaltered.
  • threshold:Threshold
    Threshold filter that allows only frequency components whose amplitudes are between the lower threshold value and the upper threshold value to pass.
Window Type window

Input

int

0
 Specify the window type for 2D FFT filters. When Filter Type is Threshold, Window Type will not be shown in the dialog.

Option list:

  • butterworth:Butterworth
    2D Butterworth filter window.
  • ideal: Ideal
    2D Ideal filter window.
  • gaussian:Gaussian
    2D Gaussian filter window.
  • blackman:Blackman
    2D Blackman filter window.
Truncate Window zerocut

Input

int

0
 This option is available only when Window Type is Blackman. It decides whether to perform zero cutoff.
Order order

Input

int

1
 The filter order, which is a positive integer number. This option is available only when Window Type is Butterworth.
Specify Cutoff By type

Input

int

1
 Specify a way to define the cutoff value. When Window Type is Blackman, Specify Cutoff By will not be shown.

Option list:

  • fraction:Fraction
    It means to define cutoff frequency by Fourier Pixel. It can be any positive number of double type.
  • pixel:Fourier Pixel
    It means to define cutoff frequency by Fraction. The cutoff value should be between 0 and 0.5.
  • wavelength: Wave-length
    It means to define cutoff frequency by Wavelength. The cutoff value should be greater than 0.
  • hertz: Hertz
    It means to define cutoff frequency by Hertz. The cutoff value needs to be greater than 0.
Cutoff Value cutoff

Input

double

3
 This option is available only when Filter Type is either Low Pass or High Pass. It specifies the cutoff value.
Lower Cutoff Value lowercut

Input

double

3
 This option is available only when Filter Type is either Band Pass or Band Block. It specifies the lower cutoff value.
Upper Cutoff Value uppercut

Input

double

10
 This option is available only when Filter Type is either Band Pass or Band Block. It specifies the upper cutoff value.
Lower Threshold lowerthre

Input

double

0
 This option is available only when Filter Type is Threshold. It specifies the lower threshold value. The value should be between 0 and 1.
Upper Threshold upperthre

Input

double

1
 This option is available only when Filter Type is Threshold. It specifies the upper threshold value. The value should be between 0 and 1. Upper Threshold should be greater than Lower Threshold.
Output Matrix om

Output

MatrixObject

<new>
 Specify the output matrix, which has been processed by 2D FFT Filters analysis.

See the syntax here.

Description

For more information, please refer to our User Guide.

Related X-Functions

fft filters

Keywords:fourier, fft, window, band, block, threshold