HALCON 21.05.0.0 / HALCON Operator Reference / Filters / FFT
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gen_gaborgen_gaborGenGaborGenGaborgen_gabor (Operator)

Name

gen_gaborgen_gaborGenGaborGenGaborgen_gabor — Generate a Gabor filter.

Signature

gen_gabor( : ImageFilter : Angle, Frequency, Bandwidth, Orientation, Norm, Mode, Width, Height : )

Herror gen_gabor(Hobject* ImageFilter, double Angle, double Frequency, double Bandwidth, double Orientation, const char* Norm, const char* Mode, const Hlong Width, const Hlong Height)

Herror T_gen_gabor(Hobject* ImageFilter, const Htuple Angle, const Htuple Frequency, const Htuple Bandwidth, const Htuple Orientation, const Htuple Norm, const Htuple Mode, const Htuple Width, const Htuple Height)

void GenGabor(HObject* ImageFilter, const HTuple& Angle, const HTuple& Frequency, const HTuple& Bandwidth, const HTuple& Orientation, const HTuple& Norm, const HTuple& Mode, const HTuple& Width, const HTuple& Height)

void HImage::GenGabor(double Angle, double Frequency, double Bandwidth, double Orientation, const HString& Norm, const HString& Mode, Hlong Width, Hlong Height)

void HImage::GenGabor(double Angle, double Frequency, double Bandwidth, double Orientation, const char* Norm, const char* Mode, Hlong Width, Hlong Height)

void HImage::GenGabor(double Angle, double Frequency, double Bandwidth, double Orientation, const wchar_t* Norm, const wchar_t* Mode, Hlong Width, Hlong Height)   (Windows only)

static void HOperatorSet.GenGabor(out HObject imageFilter, HTuple angle, HTuple frequency, HTuple bandwidth, HTuple orientation, HTuple norm, HTuple mode, HTuple width, HTuple height)

void HImage.GenGabor(double angle, double frequency, double bandwidth, double orientation, string norm, string mode, int width, int height)

def gen_gabor(angle: float, frequency: float, bandwidth: float, orientation: float, norm: str, mode: str, width: int, height: int) -> HObject

Description

gen_gaborgen_gaborGenGaborGenGaborGenGaborgen_gabor generates a Gabor filter with a user-definable bandpass frequency range and sign for the Hilbert transform. This is done by calculating a symmetrical filter in the frequency domain, which can be adapted by the parameters AngleAngleAngleAngleangleangle, FrequencyFrequencyFrequencyFrequencyfrequencyfrequency, BandwidthBandwidthBandwidthBandwidthbandwidthbandwidth and OrientationOrientationOrientationOrientationorientationorientation such that a certain frequency band and a certain direction range in the spatial domain is filtered out in the frequency domain.

The parameters FrequencyFrequencyFrequencyFrequencyfrequencyfrequency (central frequency = distance from the DC term) and OrientationOrientationOrientationOrientationorientationorientation (direction) determine the center of the filter. Larger values of FrequencyFrequencyFrequencyFrequencyfrequencyfrequency result in higher frequencies being passed. A value of 0 for OrientationOrientationOrientationOrientationorientationorientation generates a horizontally oriented “crescent” (the bulge of the crescent points upward). Higher values of OrientationOrientationOrientationOrientationorientationorientation result in the counterclockwise rotation of the crescent.

The parameters AngleAngleAngleAngleangleangle and BandwidthBandwidthBandwidthBandwidthbandwidthbandwidth are used to determine the range of frequencies and angles being passed by the filter. The larger AngleAngleAngleAngleangleangle is, the smaller the range of angles passed by the filter gets (because the “crescent” gets narrower). The larger BandwidthBandwidthBandwidthBandwidthbandwidthbandwidth is, the smaller the frequency band being passed gets (because the “crescent” gets thinner).

To achieve a maximum overall efficiency of the filtering operation, the parameter NormNormNormNormnormnorm can be used to specify the normalization factor of the filter. If fft_genericfft_genericFftGenericFftGenericFftGenericfft_generic and NormNormNormNormnormnorm = 'n'"n""n""n""n""n" is used the normalization in the FFT can be avoided. ModeModeModeModemodemode can be used to determine where the DC term of the filter lies. If fft_genericfft_genericFftGenericFftGenericFftGenericfft_generic is used, 'dc_edge'"dc_edge""dc_edge""dc_edge""dc_edge""dc_edge" can be used to gain efficiency. If fft_imagefft_imageFftImageFftImageFftImagefft_image and fft_image_invfft_image_invFftImageInvFftImageInvFftImageInvfft_image_inv are used for filtering, NormNormNormNormnormnorm = 'none'"none""none""none""none""none" and ModeModeModeModemodemode = 'dc_center'"dc_center""dc_center""dc_center""dc_center""dc_center" must be used. Note that gen_gaborgen_gaborGenGaborGenGaborGenGaborgen_gabor cannot create a filter that can be used with rft_genericrft_genericRftGenericRftGenericRftGenericrft_generic.

The resulting image is a two-channel real-image, containing the Gabor filter in the first channel and the corresponding Hilbert filter in the second channel.

Execution Information

Parameters

ImageFilterImageFilterImageFilterImageFilterimageFilterimage_filter (output_object)  multichannel-image → objectHImageHObjectHImageHobject * (real)

Gabor and Hilbert filter.

AngleAngleAngleAngleangleangle (input_control)  real → HTuplefloatHTupleHtuple (real) (double) (double) (double)

Angle range, inversely proportional to the range of orientations.

Default value: 1.4

Suggested values: 1.0, 1.2, 1.4, 1.6, 2.0, 2.5, 3.0, 5.0, 6.0, 10.0, 20.0, 30.0, 50.0, 70.0, 100.0

Typical range of values: 1.0 ≤ Angle Angle Angle Angle angle angle ≤ 500.0

Minimum increment: 0.001

Recommended increment: 0.1

FrequencyFrequencyFrequencyFrequencyfrequencyfrequency (input_control)  real → HTuplefloatHTupleHtuple (real) (double) (double) (double)

Distance of the center of the filter to the DC term.

Default value: 0.4

Suggested values: 0.0, 0.05, 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, 0.50, 0.55, 0.60, 0.65, 0.699

Typical range of values: 0.0 ≤ Frequency Frequency Frequency Frequency frequency frequency ≤ 0.7

Minimum increment: 0.00001

Recommended increment: 0.005

BandwidthBandwidthBandwidthBandwidthbandwidthbandwidth (input_control)  real → HTuplefloatHTupleHtuple (real) (double) (double) (double)

Bandwidth range, inversely proportional to the range of frequencies being passed.

Default value: 1.0

Suggested values: 0.1, 0.3, 0.7, 1.0, 1.5, 2.0, 3.0, 5.0, 7.0, 10.0, 15.0, 20.0, 30.0, 50.0

Typical range of values: 0.05 ≤ Bandwidth Bandwidth Bandwidth Bandwidth bandwidth bandwidth ≤ 100.0

Minimum increment: 0.001

Recommended increment: 0.1

OrientationOrientationOrientationOrientationorientationorientation (input_control)  real → HTuplefloatHTupleHtuple (real) (double) (double) (double)

Angle of the principal orientation.

Default value: 1.5

Suggested values: 0.0, 0.2, 0.4, 0.6, 0.8, 1.0, 1.2, 1.4, 1.6, 1.8, 2.0, 2.2, 2.4, 2.6, 2.8, 3.0, 3.14

Typical range of values: 0.0 ≤ Orientation Orientation Orientation Orientation orientation orientation ≤ 3.1416

Minimum increment: 0.0001

Recommended increment: 0.05

NormNormNormNormnormnorm (input_control)  string → HTuplestrHTupleHtuple (string) (string) (HString) (char*)

Normalizing factor of the filter.

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

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

ModeModeModeModemodemode (input_control)  string → HTuplestrHTupleHtuple (string) (string) (HString) (char*)

Location of the DC term in the frequency domain.

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

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

WidthWidthWidthWidthwidthwidth (input_control)  integer → HTupleintHTupleHtuple (integer) (int / long) (Hlong) (Hlong)

Width of the image (filter).

Default value: 512

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

HeightHeightHeightHeightheightheight (input_control)  integer → HTupleintHTupleHtuple (integer) (int / long) (Hlong) (Hlong)

Height of the image (filter).

Default value: 512

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

Example (HDevelop)

gen_gabor(Filter,1.4,0.4,1.0,1.5,'n','dc_edge',512,512)
fft_generic(Image,ImageFFT,'to_freq',-1,'none','dc_edge','complex')
convol_gabor(ImageFFT,Filter,Gabor,Hilbert)
fft_generic(Gabor,GaborInv,'from_freq',1,'none','dc_edge','byte')
fft_generic(Hilbert,HilbertInv,'from_freq',1,'none','dc_edge','byte')
energy_gabor(GaborInv,HilbertInv,Energy)

Result

gen_gaborgen_gaborGenGaborGenGaborGenGaborgen_gabor returns TRUE if all parameters are correct. If necessary, an exception is raised.

Possible Predecessors

fft_imagefft_imageFftImageFftImageFftImagefft_image, fft_genericfft_genericFftGenericFftGenericFftGenericfft_generic

Possible Successors

convol_gaborconvol_gaborConvolGaborConvolGaborConvolGaborconvol_gabor

Alternatives

gen_bandpassgen_bandpassGenBandpassGenBandpassGenBandpassgen_bandpass, gen_bandfiltergen_bandfilterGenBandfilterGenBandfilterGenBandfiltergen_bandfilter, gen_highpassgen_highpassGenHighpassGenHighpassGenHighpassgen_highpass, gen_lowpassgen_lowpassGenLowpassGenLowpassGenLowpassgen_lowpass

See also

fft_image_invfft_image_invFftImageInvFftImageInvFftImageInvfft_image_inv, energy_gaborenergy_gaborEnergyGaborEnergyGaborEnergyGaborenergy_gabor

Module

Foundation

ClassesClasses | | Operators
HALCON Operator Reference 21.05.0.0 Copyright © 1996-2021 MVTec Software GmbH
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