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_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