gen_derivative_filtergen_derivative_filtergen_derivative_filterGenDerivativeFilterGenDerivativeFilter (Operator)

Name

gen_derivative_filtergen_derivative_filtergen_derivative_filterGenDerivativeFilterGenDerivativeFilter — Generate a derivative filter in the frequency domain.

Signature

Description

gen_derivative_filtergen_derivative_filtergen_derivative_filterGenDerivativeFilterGenDerivativeFilter generates a derivative filter in the frequency domain. The derivative to be computed is determined by DerivativeDerivativeDerivativeDerivativederivative. ExponentExponentExponentExponentexponent specifies the exponent used in the reverse transform. It must be set to the same value that is used in fft_genericfft_genericfft_genericFftGenericFftGeneric. If fft_image_invfft_image_invfft_image_invFftImageInvFftImageInv is used in the reverse transform, ExponentExponentExponentExponentexponent = 1 must be used. However, since the derivative image typically contains negative values, fft_genericfft_genericfft_genericFftGenericFftGeneric should always be used for the reverse transform. 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_genericfft_genericFftGenericFftGeneric 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_genericfft_genericFftGenericFftGeneric is used, 'dc_edge'"dc_edge""dc_edge""dc_edge""dc_edge" can be used to gain efficiency. If fft_imagefft_imagefft_imageFftImageFftImage and fft_image_invfft_image_invfft_image_invFftImageInvFftImageInv 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_genericrft_genericRftGenericRftGeneric is used, ModeModeModeModemode = 'rft'"rft""rft""rft""rft" must be used.

Parallelization

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

Parameters

Example (HDevelop)

* Generate a smoothed derivative filter.
gen_gauss_filter (ImageGauss, Sigma, Sigma, 0, 'n', 'dc_edge', 512, 512)
convert_image_type (ImageGauss, ImageGaussComplex, 'complex')
gen_derivative_filter (ImageDerivX, 'x', 1, 'none', 'dc_edge', 512, 512)
mult_image (ImageGaussComplex, ImageDerivX, ImageDerivXGauss, 1, 0)
* Filter an image with the smoothed derivative filter.
fft_generic (Image, ImageFFT, 'to_freq', -1, 'none', 'dc_edge', 'complex')
convol_fft (ImageFFT, ImageDerivXGauss, Filtered)
fft_generic (Filtered, ImageX, 'from_freq', 1, 'none', 'dc_edge', 'real')

Result

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

Possible Predecessors

fft_imagefft_imagefft_imageFftImageFftImage, fft_genericfft_genericfft_genericFftGenericFftGeneric, rft_genericrft_genericrft_genericRftGenericRftGeneric

Possible Successors

convol_fftconvol_fftconvol_fftConvolFftConvolFft

See also

fft_image_invfft_image_invfft_image_invFftImageInvFftImageInv, gen_gauss_filtergen_gauss_filtergen_gauss_filterGenGaussFilterGenGaussFilter, gen_mean_filtergen_mean_filtergen_mean_filterGenMeanFilterGenMeanFilter, gen_lowpassgen_lowpassgen_lowpassGenLowpassGenLowpass, gen_bandpassgen_bandpassgen_bandpassGenBandpassGenBandpass, gen_bandfiltergen_bandfiltergen_bandfilterGenBandfilterGenBandfilter, gen_highpassgen_highpassgen_highpassGenHighpassGenHighpass

Module

Foundation