gen_derivative_filtergen_derivative_filterGenDerivativeFilterGenDerivativeFilter (Operator)


gen_derivative_filtergen_derivative_filterGenDerivativeFilterGenDerivativeFilter — Generate a derivative filter in the frequency domain.


gen_derivative_filter( : ImageDerivative : Derivative, Exponent, Norm, Mode, Width, Height : )

Herror gen_derivative_filter(Hobject* ImageDerivative, const char* Derivative, const Hlong Exponent, const char* Norm, const char* Mode, const Hlong Width, const Hlong Height)

Herror T_gen_derivative_filter(Hobject* ImageDerivative, const Htuple Derivative, const Htuple Exponent, const Htuple Norm, const Htuple Mode, const Htuple Width, const Htuple Height)

void GenDerivativeFilter(HObject* ImageDerivative, const HTuple& Derivative, const HTuple& Exponent, const HTuple& Norm, const HTuple& Mode, const HTuple& Width, const HTuple& Height)

void HImage::GenDerivativeFilter(const HString& Derivative, Hlong Exponent, const HString& Norm, const HString& Mode, Hlong Width, Hlong Height)

void HImage::GenDerivativeFilter(const char* Derivative, Hlong Exponent, const char* Norm, const char* Mode, Hlong Width, Hlong Height)

void HImage::GenDerivativeFilter(const wchar_t* Derivative, Hlong Exponent, const wchar_t* Norm, const wchar_t* Mode, Hlong Width, Hlong Height)   (Windows only)

static void HOperatorSet.GenDerivativeFilter(out HObject imageDerivative, HTuple derivative, HTuple exponent, HTuple norm, HTuple mode, HTuple width, HTuple height)

void HImage.GenDerivativeFilter(string derivative, int exponent, string norm, string mode, int width, int height)


gen_derivative_filtergen_derivative_filterGenDerivativeFilterGenDerivativeFilterGenDerivativeFilter 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_genericFftGenericFftGenericFftGeneric. If fft_image_invfft_image_invFftImageInvFftImageInvFftImageInv is used in the reverse transform, ExponentExponentExponentExponentexponent = 1 must be used. However, since the derivative image typically contains negative values, fft_genericfft_genericFftGenericFftGenericFftGeneric 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_genericFftGenericFftGenericFftGeneric 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_genericFftGenericFftGenericFftGeneric is used, 'dc_edge'"dc_edge""dc_edge""dc_edge""dc_edge" can be used to gain efficiency. If fft_imagefft_imageFftImageFftImageFftImage and fft_image_invfft_image_invFftImageInvFftImageInvFftImageInv 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_genericRftGenericRftGenericRftGeneric is used, ModeModeModeModemode = 'rft'"rft""rft""rft""rft" must be used.

Execution Information


ImageDerivativeImageDerivativeImageDerivativeImageDerivativeimageDerivative (output_object)  image objectHImageHImageHobject * (complex)

Derivative filter as image in the frequency domain.

DerivativeDerivativeDerivativeDerivativederivative (input_control)  string HTupleHTupleHtuple (string) (string) (HString) (char*)

Derivative to be computed.

Default value: 'x' "x" "x" "x" "x"

Suggested values: 'x'"x""x""x""x", 'y'"y""y""y""y", 'xx'"xx""xx""xx""xx", 'xy'"xy""xy""xy""xy", 'yy'"yy""yy""yy""yy", 'xxx'"xxx""xxx""xxx""xxx", 'xxy'"xxy""xxy""xxy""xxy", 'xyy'"xyy""xyy""xyy""xyy", 'yyy'"yyy""yyy""yyy""yyy"

ExponentExponentExponentExponentexponent (input_control)  integer HTupleHTupleHtuple (integer) (int / long) (Hlong) (Hlong)

Exponent used in the reverse transform.

Default value: 1

Suggested values: -1, 1

NormNormNormNormnorm (input_control)  string HTupleHTupleHtuple (string) (string) (HString) (char*)

Normalizing factor of the filter.

Default value: 'none' "none" "none" "none" "none"

List of values: 'n'"n""n""n""n", 'none'"none""none""none""none"

ModeModeModeModemode (input_control)  string HTupleHTupleHtuple (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"

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 HTupleHTupleHtuple (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

HeightHeightHeightHeightheight (input_control)  integer HTupleHTupleHtuple (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)

* 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')


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

Possible Predecessors

fft_imagefft_imageFftImageFftImageFftImage, fft_genericfft_genericFftGenericFftGenericFftGeneric, rft_genericrft_genericRftGenericRftGenericRftGeneric

Possible Successors


See also

fft_image_invfft_image_invFftImageInvFftImageInvFftImageInv, gen_gauss_filtergen_gauss_filterGenGaussFilterGenGaussFilterGenGaussFilter, gen_mean_filtergen_mean_filterGenMeanFilterGenMeanFilterGenMeanFilter, gen_lowpassgen_lowpassGenLowpassGenLowpassGenLowpass, gen_bandpassgen_bandpassGenBandpassGenBandpassGenBandpass, gen_bandfiltergen_bandfilterGenBandfilterGenBandfilterGenBandfilter, gen_highpassgen_highpassGenHighpassGenHighpassGenHighpass