Operator Reference

HALCON Operator Reference / Filters / FFT
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gen_bandfiltergen_bandfilterGenBandfilterGenBandfiltergen_bandfilter (Operator)

gen_bandfiltergen_bandfilterGenBandfilterGenBandfiltergen_bandfilter — Generate an ideal band filter.

Signature

gen_bandfilter( : ImageFilter : MinFrequency, MaxFrequency, Norm, Mode, Width, Height : )

Herror gen_bandfilter(Hobject* ImageFilter, double MinFrequency, double MaxFrequency, const char* Norm, const char* Mode, const Hlong Width, const Hlong Height)

Herror T_gen_bandfilter(Hobject* ImageFilter, const Htuple MinFrequency, const Htuple MaxFrequency, const Htuple Norm, const Htuple Mode, const Htuple Width, const Htuple Height)

void GenBandfilter(HObject* ImageFilter, const HTuple& MinFrequency, const HTuple& MaxFrequency, const HTuple& Norm, const HTuple& Mode, const HTuple& Width, const HTuple& Height)

void HImage::GenBandfilter(double MinFrequency, double MaxFrequency, const HString& Norm, const HString& Mode, Hlong Width, Hlong Height)

void HImage::GenBandfilter(double MinFrequency, double MaxFrequency, const char* Norm, const char* Mode, Hlong Width, Hlong Height)

void HImage::GenBandfilter(double MinFrequency, double MaxFrequency, const wchar_t* Norm, const wchar_t* Mode, Hlong Width, Hlong Height)   ( Windows only)

static void HOperatorSet.GenBandfilter(out HObject imageFilter, HTuple minFrequency, HTuple maxFrequency, HTuple norm, HTuple mode, HTuple width, HTuple height)

void HImage.GenBandfilter(double minFrequency, double maxFrequency, string norm, string mode, int width, int height)

def gen_bandfilter(min_frequency: float, max_frequency: float, norm: str, mode: str, width: int, height: int) -> HObject

Description

gen_bandfiltergen_bandfilterGenBandfilterGenBandfiltergen_bandfilter generates an ideal band filter in the frequency domain. The parameters MinFrequencyMinFrequencyMinFrequencyminFrequencymin_frequency and MaxFrequencyMaxFrequencyMaxFrequencymaxFrequencymax_frequency determine the cutoff frequencies 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., MinFrequencyMinFrequencyMinFrequencyminFrequencymin_frequency and MaxFrequencyMaxFrequencyMaxFrequencymaxFrequencymax_frequency 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_genericFftGenericFftGenericfft_generic 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_genericFftGenericFftGenericfft_generic is used, 'dc_edge'"dc_edge""dc_edge""dc_edge""dc_edge" can be used to gain efficiency. If fft_imagefft_imageFftImageFftImagefft_image and fft_image_invfft_image_invFftImageInvFftImageInvfft_image_inv 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_genericRftGenericRftGenericrft_generic is used, ModeModeModemodemode = 'rft'"rft""rft""rft""rft" must be used. The resulting image contains an annulus with the value 0, and a value determined by the normalization outside of this annulus.

Execution Information

  • Multithreading type: reentrant (runs in parallel with non-exclusive operators).
  • Multithreading scope: global (may be called from any thread).
  • Processed without parallelization.

Parameters

ImageFilterImageFilterImageFilterimageFilterimage_filter (output_object)  image → objectHImageHObjectHObjectHobject * (real)

Band filter in the frequency domain.

MinFrequencyMinFrequencyMinFrequencyminFrequencymin_frequency (input_control)  real → HTuplefloatHTupleHtuple (real) (double) (double) (double)

Minimum frequency.

Default: 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: MinFrequency >= 0

MaxFrequencyMaxFrequencyMaxFrequencymaxFrequencymax_frequency (input_control)  real → HTuplefloatHTupleHtuple (real) (double) (double) (double)

Maximum frequency.

Default: 0.2

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: MaxFrequency >= 0 && MaxFrequency >= MinFrequency

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

Normalizing factor of the filter.

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

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

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

Location of the DC term in the frequency domain.

Default: '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 → HTupleintHTupleHtuple (integer) (int / long) (Hlong) (Hlong)

Width of the image (filter).

Default: 512

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

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

Height of the image (filter).

Default: 512

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

Example (HDevelop)

* Filtering with maximum efficiency with fft_generic.
gen_bandpass(Bandfilter,0.2,0.4,'n','dc_edge',Width,Height)
fft_generic(Image,ImageFFT,'to_freq',-1,'none','dc_edge','complex')
convol_fft(ImageFFT,Bandfilter,ImageConvol)
fft_generic(ImageConvol,ImageResult,'from_freq',1,'none','dc_edge','byte')

Result

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

Possible Successors

convol_fftconvol_fftConvolFftConvolFftconvol_fft

Alternatives

gen_circlegen_circleGenCircleGenCirclegen_circle, paint_regionpaint_regionPaintRegionPaintRegionpaint_region

See also

gen_highpassgen_highpassGenHighpassGenHighpassgen_highpass, gen_lowpassgen_lowpassGenLowpassGenLowpassgen_lowpass, gen_bandpassgen_bandpassGenBandpassGenBandpassgen_bandpass, gen_gauss_filtergen_gauss_filterGenGaussFilterGenGaussFiltergen_gauss_filter, gen_mean_filtergen_mean_filterGenMeanFilterGenMeanFiltergen_mean_filter, gen_derivative_filtergen_derivative_filterGenDerivativeFilterGenDerivativeFiltergen_derivative_filter

Module

Foundation

ClassesClasses | | Operators