gen_bandfiltergen_bandfilterGenBandfilterGenBandfiltergen_bandfilter (Operator)
Name
gen_bandfiltergen_bandfilterGenBandfilterGenBandfiltergen_bandfilter — Generate an ideal band filter.
Signature
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)
Description
gen_bandfiltergen_bandfilterGenBandfilterGenBandfilterGenBandfiltergen_bandfilter generates an ideal band filter in the
frequency domain. The parameters MinFrequencyMinFrequencyMinFrequencyMinFrequencyminFrequencymin_frequency and
MaxFrequencyMaxFrequencyMaxFrequencyMaxFrequencymaxFrequencymax_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 WidthWidthWidthWidthwidthwidth
x HeightHeightHeightHeightheightheight, i.e., MinFrequencyMinFrequencyMinFrequencyMinFrequencyminFrequencymin_frequency and
MaxFrequencyMaxFrequencyMaxFrequencyMaxFrequencymaxFrequencymax_frequency 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 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
ImageFilterImageFilterImageFilterImageFilterimageFilterimage_filter (output_object) image → objectHImageHObjectHImageHobject * (real)
Band filter in the frequency domain.
MinFrequencyMinFrequencyMinFrequencyMinFrequencyminFrequencymin_frequency (input_control) real → HTuplefloatHTupleHtuple (real) (double) (double) (double)
Minimum 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: MinFrequency >= 0
MaxFrequencyMaxFrequencyMaxFrequencyMaxFrequencymaxFrequencymax_frequency (input_control) real → HTuplefloatHTupleHtuple (real) (double) (double) (double)
Maximum frequency.
Default value: 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
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_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_bandfilterGenBandfilterGenBandfilterGenBandfiltergen_bandfilter returns TRUE if all parameters are
correct. If necessary, an exception is raised.
Possible Successors
convol_fftconvol_fftConvolFftConvolFftConvolFftconvol_fft
Alternatives
gen_circlegen_circleGenCircleGenCircleGenCirclegen_circle,
paint_regionpaint_regionPaintRegionPaintRegionPaintRegionpaint_region
See also
gen_highpassgen_highpassGenHighpassGenHighpassGenHighpassgen_highpass,
gen_lowpassgen_lowpassGenLowpassGenLowpassGenLowpassgen_lowpass,
gen_bandpassgen_bandpassGenBandpassGenBandpassGenBandpassgen_bandpass,
gen_gauss_filtergen_gauss_filterGenGaussFilterGenGaussFilterGenGaussFiltergen_gauss_filter,
gen_mean_filtergen_mean_filterGenMeanFilterGenMeanFilterGenMeanFiltergen_mean_filter,
gen_derivative_filtergen_derivative_filterGenDerivativeFilterGenDerivativeFilterGenDerivativeFiltergen_derivative_filter
Module
Foundation