gen_lowpassgen_lowpassGenLowpassGenLowpassgen_lowpass (Operator)

Name

gen_lowpassgen_lowpassGenLowpassGenLowpassgen_lowpass — 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)

void GenLowpass(HObject* ImageLowpass, const HTuple& Frequency, const HTuple& Norm, const HTuple& Mode, const HTuple& Width, const HTuple& Height)

void HImage::GenLowpass(double Frequency, const HString& Norm, const HString& Mode, Hlong Width, Hlong Height)

void HImage::GenLowpass(double Frequency, const char* Norm, const char* Mode, Hlong Width, Hlong Height)

void HImage::GenLowpass(double Frequency, const wchar_t* Norm, const wchar_t* Mode, Hlong Width, Hlong Height)   (Windows only)

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)

def gen_lowpass(frequency: float, norm: str, mode: str, width: int, height: int) -> HObject

Description

gen_lowpassgen_lowpassGenLowpassGenLowpassGenLowpassgen_lowpass generates an ideal lowpass filter in the frequency domain. The parameter FrequencyFrequencyFrequencyFrequencyfrequencyfrequency 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 WidthWidthWidthWidthwidthwidth x HeightHeightHeightHeightheightheight, i.e., FrequencyFrequencyFrequencyFrequencyfrequencyfrequency should lie between 0 and 1. 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 or whether the filter should be used in the real-valued FFT. 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. If rft_genericrft_genericRftGenericRftGenericRftGenericrft_generic is used, ModeModeModeModemodemode = 'rft'"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.

Execution Information

Parameters

ImageLowpassImageLowpassImageLowpassImageLowpassimageLowpassimage_lowpass (output_object)  image objectHImageHObjectHImageHobject * (real)

Lowpass filter in the frequency domain.

FrequencyFrequencyFrequencyFrequencyfrequencyfrequency (input_control)  real HTuplefloatHTupleHtuple (real) (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

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", 'rft'"rft""rft""rft""rft""rft"

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)

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

Possible Successors

convol_fftconvol_fftConvolFftConvolFftConvolFftconvol_fft

See also

gen_highpassgen_highpassGenHighpassGenHighpassGenHighpassgen_highpass, gen_bandpassgen_bandpassGenBandpassGenBandpassGenBandpassgen_bandpass, gen_bandfiltergen_bandfilterGenBandfilterGenBandfilterGenBandfiltergen_bandfilter, gen_gauss_filtergen_gauss_filterGenGaussFilterGenGaussFilterGenGaussFiltergen_gauss_filter, gen_mean_filtergen_mean_filterGenMeanFilterGenMeanFilterGenMeanFiltergen_mean_filter, gen_derivative_filtergen_derivative_filterGenDerivativeFilterGenDerivativeFilterGenDerivativeFiltergen_derivative_filter

Module

Foundation