HALCON Reference Manual 10.0.2
Table of Contents / Filters / FFT ClassesClassesClasses | | | Operators

gen_lowpassgen_lowpassgen_lowpassGenLowpassGenLowpass (Operator)

Name

gen_lowpassgen_lowpassgen_lowpassGenLowpassGenLowpass — Generate an ideal lowpass filter.

Signature

gen_lowpass( : ImageLowpass : Frequency, Norm, Mode, Width, Height : )

Herror gen_lowpass(Hobject* ImageLowpass, double Frequency, const char* Norm, const char* Mode, const Hlong Width, const Hlong Height)

Herror T_gen_lowpass(Hobject* ImageLowpass, const Htuple Frequency, const Htuple Norm, const Htuple Mode, const Htuple Width, const Htuple Height)

Herror gen_lowpass(Hobject* ImageLowpass, const HTuple& Frequency, const HTuple& Norm, const HTuple& Mode, const HTuple& Width, const HTuple& Height)

HImage HImage::GenLowpass(const HTuple& Frequency, const HTuple& Norm, const HTuple& Mode, const HTuple& Width, const HTuple& Height)

void HOperatorSetX.GenLowpass(
[out] IHUntypedObjectX** ImageLowpass, [in] VARIANT Frequency, [in] VARIANT Norm, [in] VARIANT Mode, [in] VARIANT Width, [in] VARIANT Height)

void HImageX.GenLowpass(
[in] double Frequency, [in] BSTR Norm, [in] BSTR Mode, [in] Hlong Width, [in] Hlong Height)

static void HOperatorSet.GenLowpass(out HObject imageLowpass, HTuple frequency, HTuple norm, HTuple mode, HTuple width, HTuple height)

void HImage.GenLowpass(double frequency, string norm, string mode, int width, int height)

Description

gen_lowpassgen_lowpassgen_lowpassGenLowpassGenLowpass generates an ideal lowpass filter in the frequency domain. The parameter FrequencyFrequencyFrequencyFrequencyfrequency determines the cutoff frequency of the filter as a fraction of the maximum (horizontal and vertical) frequency that can be represented in an image of size WidthWidthWidthWidthwidth x HeightHeightHeightHeightheight, i.e., FrequencyFrequencyFrequencyFrequencyfrequency should lie between 0 and 1. To achieve a maximum overall efficiency of the filtering operation, the parameter NormNormNormNormnorm can be used to specify the normalization factor of the filter. If fft_genericfft_genericfft_genericFftGenericFftGeneric and NormNormNormNormnorm = 'n'"n""n""n""n" is used the normalization in the FFT can be avoided. ModeModeModeModemode can be used to determine where the DC term of the filter lies or whether the filter should be used in the real-valued FFT. If fft_genericfft_genericfft_genericFftGenericFftGeneric is used, 'dc_edge'"dc_edge""dc_edge""dc_edge""dc_edge" can be used to gain efficiency. If fft_imagefft_imagefft_imageFftImageFftImage and fft_image_invfft_image_invfft_image_invFftImageInvFftImageInv are used for filtering, NormNormNormNormnorm = 'none'"none""none""none""none" and ModeModeModeModemode = 'dc_center'"dc_center""dc_center""dc_center""dc_center" must be used. If rft_genericrft_genericrft_genericRftGenericRftGeneric is used, ModeModeModeModemode = 'rft'"rft""rft""rft""rft" must be used. The resulting image has an inner part with the value set to the normalization factor, and an outer part with the value 0.

Parallelization

Parameters

ImageLowpassImageLowpassImageLowpassImageLowpassimageLowpass (output_object)  image → objectHImageHImageHImageXHobject * (real)

Lowpass filter in the frequency domain.

FrequencyFrequencyFrequencyFrequencyfrequency (input_control)  real → HTupleHTupleVARIANTHtuple (real) (double) (double) (double) (double)

Cutoff frequency.

Default value: 0.1

Suggested values: 0.0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0

Restriction: Frequency >= 0

NormNormNormNormnorm (input_control)  string → HTupleHTupleVARIANTHtuple (string) (string) (char*) (BSTR) (char*)

Normalizing factor of the filter.

Default value: 'none' "none" "none" "none" "none"

List of values: 'none'"none""none""none""none", 'n'"n""n""n""n"

ModeModeModeModemode (input_control)  string → HTupleHTupleVARIANTHtuple (string) (string) (char*) (BSTR) (char*)

Location of the DC term in the frequency domain.

Default value: 'dc_center' "dc_center" "dc_center" "dc_center" "dc_center"

List of values: 'dc_center'"dc_center""dc_center""dc_center""dc_center", 'dc_edge'"dc_edge""dc_edge""dc_edge""dc_edge", 'rft'"rft""rft""rft""rft"

WidthWidthWidthWidthwidth (input_control)  integer → HTupleHTupleVARIANTHtuple (integer) (int / long) (Hlong) (Hlong) (Hlong)

Width of the image (filter).

Default value: 512

List of values: 128, 160, 192, 256, 320, 384, 512, 640, 768, 1024, 2048, 4096, 8192

HeightHeightHeightHeightheight (input_control)  integer → HTupleHTupleVARIANTHtuple (integer) (int / long) (Hlong) (Hlong) (Hlong)

Height of the image (filter).

Default value: 512

List of values: 120, 128, 144, 240, 256, 288, 480, 512, 576, 1024, 2048, 4096, 8192

Example (C)

/* Filtering with maximum efficiency with fft_generic. */
gen_lowpass(Lowpass,0.2,'n','dc_edge',Width,Height)
fft_generic(Image,ImageFFT,'to_freq',-1,'none','dc_edge','complex')
convol_fft(ImageFFT,Lowpass:ImageConvol)
fft_generic(ImageConvol,ImageResult,'from_freq',1,'none','dc_edge','byte')

Result

gen_lowpassgen_lowpassgen_lowpassGenLowpassGenLowpass returns 2 (H_MSG_TRUE) if all parameters are correct. If necessary, an exception is raised.

Possible Successors

convol_fftconvol_fftconvol_fftConvolFftConvolFft

See also

gen_highpassgen_highpassgen_highpassGenHighpassGenHighpass, gen_bandpassgen_bandpassgen_bandpassGenBandpassGenBandpass, gen_bandfiltergen_bandfiltergen_bandfilterGenBandfilterGenBandfilter, gen_gauss_filtergen_gauss_filtergen_gauss_filterGenGaussFilterGenGaussFilter, gen_mean_filtergen_mean_filtergen_mean_filterGenMeanFilterGenMeanFilter, gen_derivative_filtergen_derivative_filtergen_derivative_filterGenDerivativeFilterGenDerivativeFilter

Module

Foundation

Table of Contents / Filters / FFT ClassesClassesClasses | | | Operators
HALCON Reference Manual 10.0.2 Copyright © 1996-2011 MVTec Software GmbH