gen_highpassgen_highpassGenHighpassGenHighpassgen_highpass (Operator)
Name
gen_highpassgen_highpassGenHighpassGenHighpassgen_highpass — Generate an ideal highpass filter.
Signature
Herror gen_highpass(Hobject* ImageHighpass, double Frequency, const char* Norm, const char* Mode, const Hlong Width, const Hlong Height)
Herror T_gen_highpass(Hobject* ImageHighpass, const Htuple Frequency, const Htuple Norm, const Htuple Mode, const Htuple Width, const Htuple Height)
void GenHighpass(HObject* ImageHighpass, const HTuple& Frequency, const HTuple& Norm, const HTuple& Mode, const HTuple& Width, const HTuple& Height)
void HImage::GenHighpass(double Frequency, const HString& Norm, const HString& Mode, Hlong Width, Hlong Height)
void HImage::GenHighpass(double Frequency, const char* Norm, const char* Mode, Hlong Width, Hlong Height)
void HImage::GenHighpass(double Frequency, const wchar_t* Norm, const wchar_t* Mode, Hlong Width, Hlong Height)
(
Windows only)
Description
gen_highpassgen_highpassGenHighpassGenHighpassGenHighpassgen_highpass generates an ideal highpass 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 0, and an outer part with the
value determined by the normalization factor.
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
ImageHighpassImageHighpassImageHighpassImageHighpassimageHighpassimage_highpass (output_object) image → objectHImageHObjectHImageHobject * (real)
Highpass filter in the frequency domain.
FrequencyFrequencyFrequencyFrequencyfrequencyfrequency (input_control) real → HTuplefloatHTupleHtuple (real) (double) (double) (double)
Cutoff 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:
Frequency >= 0
NormNormNormNormnormnorm (input_control) string → HTuplestrHTupleHtuple (string) (string) (HString) (char*)
Normalizing factor of the filter.
Default:
'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:
'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:
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:
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_highpass(Highpass,0.2,'n','dc_edge',Width,Height)
fft_generic(Image,ImageFFT,'to_freq',-1,'none','dc_edge','complex')
convol_fft(ImageFFT,Highpass,ImageConvol)
fft_generic(ImageConvol,ImageResult,'from_freq',1,'none','dc_edge','byte')
Result
gen_highpassgen_highpassGenHighpassGenHighpassGenHighpassgen_highpass returns 2 (
H_MSG_TRUE)
if all parameters are correct.
If necessary, an exception is raised.
Possible Successors
convol_fftconvol_fftConvolFftConvolFftConvolFftconvol_fft
See also
convol_fftconvol_fftConvolFftConvolFftConvolFftconvol_fft,
gen_lowpassgen_lowpassGenLowpassGenLowpassGenLowpassgen_lowpass,
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