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Convolution filters for multi-dimensional arrays. | ![]() |
Functions | |
template<... > | |
void | convolveFFT (...) |
Convolve an array with a kernel by means of the Fourier transform. | |
template<... > | |
void | convolveFFTComplex (...) |
Convolve a complex-valued array by means of the Fourier transform. | |
template<... > | |
void | convolveFFTComplexMany (...) |
Convolve a complex-valued array with a sequence of kernels by means of the Fourier transform. | |
template<... > | |
void | convolveFFTMany (...) |
Convolve a real-valued array with a sequence of kernels by means of the Fourier transform. | |
template<... > | |
void | convolveMultiArrayOneDimension (...) |
Convolution along a single dimension of a multi-dimensional arrays. | |
template<... > | |
void | gaussianGradientMultiArray (...) |
Calculate Gaussian gradient of a multi-dimensional arrays. | |
template<... > | |
void | gaussianSmoothMultiArray (...) |
Isotropic Gaussian smoothing of a multi-dimensional arrays. | |
template<... > | |
void | hessianOfGaussianMultiArray (...) |
Calculate Hessian matrix of a N-dimensional arrays using Gaussian derivative filters. | |
template<... > | |
void | laplacianOfGaussianMultiArray (...) |
Calculate Laplacian of a N-dimensional arrays using Gaussian derivative filters. | |
template<... > | |
void | separableConvolveMultiArray (...) |
Separated convolution on multi-dimensional arrays. | |
template<... > | |
void | structureTensorMultiArray (...) |
Calculate th structure tensor of a multi-dimensional arrays. | |
template<... > | |
void | symmetricGradientMultiArray (...) |
Calculate gradient of a multi-dimensional arrays using symmetric difference filters. |
These functions realize a separable convolution on an arbitrary dimensional array that is specified by iterators (compatible to Multi-dimensional Array Iterators) and shape objects. It can therefore be applied to a wide range of data structures (vigra::MultiArrayView, vigra::MultiArray etc.).
void vigra::separableConvolveMultiArray | ( | ... | ) |
Separated convolution on multi-dimensional arrays.
This function computes a separated convolution on all dimensions of the given multi-dimensional array. Both source and destination arrays are represented by iterators, shape objects and accessors. The destination array is required to already have the correct size.
There are two variants of this functions: one takes a single kernel of type vigra::Kernel1D which is then applied to all dimensions, whereas the other requires an iterator referencing a sequence of vigra::Kernel1D objects, one for every dimension of the data. Then the first kernel in this sequence is applied to the innermost dimension (e.g. the x-dimension of an image), while the last is applied to the outermost dimension (e.g. the z-dimension in a 3D image).
This function may work in-place, which means that siter == diter
is allowed. A full-sized internal array is only allocated if working on the destination array directly would cause round-off errors (i.e. if typeid(typename NumericTraits<typename DestAccessor::value_type>::RealPromote) != typeid(typename DestAccessor::value_type)
.
If start
and stop
have non-default values, they must represent a valid subarray of the input array. The convolution is then restricted to that subarray, and it is assumed that the output array only refers to the subarray (i.e. diter
points to the element corresponding to start
).
Declarations:
pass arguments explicitly:
namespace vigra { // apply the same kernel to all dimensions template <class SrcIterator, class SrcShape, class SrcAccessor, class DestIterator, class DestAccessor, class T> void separableConvolveMultiArray(SrcIterator siter, SrcShape const & shape, SrcAccessor src, DestIterator diter, DestAccessor dest, Kernel1D<T> const & kernel, SrcShape const & start = SrcShape(), SrcShape const & stop = SrcShape()); // apply each kernel from the sequence 'kernels' in turn template <class SrcIterator, class SrcShape, class SrcAccessor, class DestIterator, class DestAccessor, class KernelIterator> void separableConvolveMultiArray(SrcIterator siter, SrcShape const & shape, SrcAccessor src, DestIterator diter, DestAccessor dest, KernelIterator kernels, SrcShape const & start = SrcShape(), SrcShape const & stop = SrcShape()); }
use argument objects in conjunction with Argument Object Factories :
namespace vigra { // apply the same kernel to all dimensions template <class SrcIterator, class SrcShape, class SrcAccessor, class DestIterator, class DestAccessor, class T> void separableConvolveMultiArray(triple<SrcIterator, SrcShape, SrcAccessor> const & source, pair<DestIterator, DestAccessor> const & dest, Kernel1D<T> const & kernel, SrcShape const & start = SrcShape(), SrcShape const & stop = SrcShape()); // apply each kernel from the sequence 'kernels' in turn template <class SrcIterator, class SrcShape, class SrcAccessor, class DestIterator, class DestAccessor, class KernelIterator> void separableConvolveMultiArray(triple<SrcIterator, SrcShape, SrcAccessor> const & source, pair<DestIterator, DestAccessor> const & dest, KernelIterator kernels, SrcShape const & start = SrcShape(), SrcShape const & stop = SrcShape()); }
Usage:
#include <vigra/multi_convolution.hxx>
MultiArray<3, unsigned char>::size_type shape(width, height, depth); MultiArray<3, unsigned char> source(shape); MultiArray<3, float> dest(shape); ... Kernel1D<float> gauss; gauss.initGaussian(sigma); // create 3 Gauss kernels, one for each dimension ArrayVector<Kernel1D<float> > kernels(3, gauss); // perform Gaussian smoothing on all dimensions separableConvolveMultiArray(srcMultiArrayRange(source), destMultiArray(dest), kernels.begin());
Required Interface:
see separableConvolveMultiArray(), in addition:
int dimension = 0;
VectorElementAccessor<DestAccessor> elementAccessor(0, dest);
void vigra::convolveMultiArrayOneDimension | ( | ... | ) |
Convolution along a single dimension of a multi-dimensional arrays.
This function computes a convolution along one dimension (specified by the parameter dim
of the given multi-dimensional array with the given kernel
. Both source and destination arrays are represented by iterators, shape objects and accessors. The destination array is required to already have the correct size.
If start
and stop
have non-default values, they must represent a valid subarray of the input array. The convolution is then restricted to that subarray, and it is assumed that the output array only refers to the subarray (i.e. diter
points to the element corresponding to start
).
This function may work in-place, which means that siter == diter
is allowed.
Declarations:
pass arguments explicitly:
namespace vigra { template <class SrcIterator, class SrcShape, class SrcAccessor, class DestIterator, class DestAccessor, class T> void convolveMultiArrayOneDimension(SrcIterator siter, SrcShape const & shape, SrcAccessor src, DestIterator diter, DestAccessor dest, unsigned int dim, vigra::Kernel1D<T> const & kernel, SrcShape const & start = SrcShape(), SrcShape const & stop = SrcShape()); }
use argument objects in conjunction with Argument Object Factories :
namespace vigra { template <class SrcIterator, class SrcShape, class SrcAccessor, class DestIterator, class DestAccessor, class T> void convolveMultiArrayOneDimension(triple<SrcIterator, SrcShape, SrcAccessor> const & source, pair<DestIterator, DestAccessor> const & dest, unsigned int dim, vigra::Kernel1D<T> const & kernel, SrcShape const & start = SrcShape(), SrcShape const & stop = SrcShape()); }
Usage:
#include <vigra/multi_convolution.hxx>
MultiArray<3, unsigned char>::size_type shape(width, height, depth); MultiArray<3, unsigned char> source(shape); MultiArray<3, float> dest(shape); ... Kernel1D<float> gauss; gauss.initGaussian(sigma); // perform Gaussian smoothing along dimensions 1 (height) convolveMultiArrayOneDimension(srcMultiArrayRange(source), destMultiArray(dest), 1, gauss);
void vigra::gaussianSmoothMultiArray | ( | ... | ) |
Isotropic Gaussian smoothing of a multi-dimensional arrays.
This function computes an isotropic convolution of the given N-dimensional array with a Gaussian filter at the given standard deviation sigma
. Both source and destination arrays are represented by iterators, shape objects and accessors. The destination array is required to already have the correct size. This function may work in-place, which means that siter == diter
is allowed. It is implemented by a call to separableConvolveMultiArray() with the appropriate kernel.
Anisotropic data should be passed with appropriate ConvolutionOptions, the parameter opt
is otherwise optional unless the parameter sigma
is left out.
Declarations:
pass arguments explicitly:
namespace vigra { template <class SrcIterator, class SrcShape, class SrcAccessor, class DestIterator, class DestAccessor> void gaussianSmoothMultiArray(SrcIterator siter, SrcShape const & shape, SrcAccessor src, DestIterator diter, DestAccessor dest, double sigma, const ConvolutionOptions<N> & opt); }
use argument objects in conjunction with Argument Object Factories :
namespace vigra { template <class SrcIterator, class SrcShape, class SrcAccessor, class DestIterator, class DestAccessor> void gaussianSmoothMultiArray(triple<SrcIterator, SrcShape, SrcAccessor> const & source, pair<DestIterator, DestAccessor> const & dest, double sigma, const ConvolutionOptions<N> & opt); }
Usage:
#include <vigra/multi_convolution.hxx>
MultiArray<3, unsigned char>::size_type shape(width, height, depth); MultiArray<3, unsigned char> source(shape); MultiArray<3, float> dest(shape); ... // perform isotropic Gaussian smoothing at scale 'sigma' gaussianSmoothMultiArray(srcMultiArrayRange(source), destMultiArray(dest), sigma);
Usage with anisotropic data:
#include <vigra/multi_convolution.hxx>
MultiArray<3, unsigned char>::size_type shape(width, height, depth); MultiArray<3, unsigned char> source(shape); MultiArray<3, float> dest(shape); TinyVector<float, 3> step_size; TinyVector<float, 3> resolution_sigmas; ... // perform anisotropic Gaussian smoothing at scale 'sigma' gaussianSmoothMultiArray(srcMultiArrayRange(source), destMultiArray(dest), sigma, ConvolutionOptions<3>().stepSize(step_size).resolutionStdDev(resolution_sigmas));
void vigra::gaussianGradientMultiArray | ( | ... | ) |
Calculate Gaussian gradient of a multi-dimensional arrays.
This function computes the Gaussian gradient of the given N-dimensional array with a sequence of first-derivative-of-Gaussian filters at the given standard deviation sigma
(differentiation is applied to each dimension in turn, starting with the innermost dimension). Both source and destination arrays are represented by iterators, shape objects and accessors. The destination array is required to have a vector valued pixel type with as many elements as the number of dimensions. This function is implemented by calls to separableConvolveMultiArray() with the appropriate kernels.
Anisotropic data should be passed with appropriate ConvolutionOptions, the parameter opt
is otherwise optional unless the parameter sigma
is left out.
Declarations:
pass arguments explicitly:
namespace vigra { template <class SrcIterator, class SrcShape, class SrcAccessor, class DestIterator, class DestAccessor> void gaussianGradientMultiArray(SrcIterator siter, SrcShape const & shape, SrcAccessor src, DestIterator diter, DestAccessor dest, double sigma, const ConvolutionOptions<N> & opt); }
use argument objects in conjunction with Argument Object Factories :
namespace vigra { template <class SrcIterator, class SrcShape, class SrcAccessor, class DestIterator, class DestAccessor> void gaussianGradientMultiArray(triple<SrcIterator, SrcShape, SrcAccessor> const & source, pair<DestIterator, DestAccessor> const & dest, double sigma, const ConvolutionOptions<N> & opt); }
Usage:
#include <vigra/multi_convolution.hxx>
MultiArray<3, unsigned char>::size_type shape(width, height, depth); MultiArray<3, unsigned char> source(shape); MultiArray<3, TinyVector<float, 3> > dest(shape); ... // compute Gaussian gradient at scale sigma gaussianGradientMultiArray(srcMultiArrayRange(source), destMultiArray(dest), sigma);
Usage with anisotropic data:
#include <vigra/multi_convolution.hxx>
MultiArray<3, unsigned char>::size_type shape(width, height, depth); MultiArray<3, unsigned char> source(shape); MultiArray<3, TinyVector<float, 3> > dest(shape); TinyVector<float, 3> step_size; TinyVector<float, 3> resolution_sigmas; ... // compute Gaussian gradient at scale sigma gaussianGradientMultiArray(srcMultiArrayRange(source), destMultiArray(dest), sigma, ConvolutionOptions<3>().stepSize(step_size).resolutionStdDev(resolution_sigmas));
Required Interface:
see separableConvolveMultiArray(), in addition:
int dimension = 0;
VectorElementAccessor<DestAccessor> elementAccessor(0, dest);
void vigra::symmetricGradientMultiArray | ( | ... | ) |
Calculate gradient of a multi-dimensional arrays using symmetric difference filters.
This function computes the gradient of the given N-dimensional array with a sequence of symmetric difference filters a (differentiation is applied to each dimension in turn, starting with the innermost dimension). Both source and destination arrays are represented by iterators, shape objects and accessors. The destination array is required to have a vector valued pixel type with as many elements as the number of dimensions. This function is implemented by calls to convolveMultiArrayOneDimension() with the symmetric difference kernel.
Anisotropic data should be passed with appropriate ConvolutionOptions, the parameter opt
is optional otherwise.
Declarations:
pass arguments explicitly:
namespace vigra { template <class SrcIterator, class SrcShape, class SrcAccessor, class DestIterator, class DestAccessor> void symmetricGradientMultiArray(SrcIterator siter, SrcShape const & shape, SrcAccessor src, DestIterator diter, DestAccessor dest, const ConvolutionOptions<N> & opt); }
use argument objects in conjunction with Argument Object Factories :
namespace vigra { template <class SrcIterator, class SrcShape, class SrcAccessor, class DestIterator, class DestAccessor> void symmetricGradientMultiArray(triple<SrcIterator, SrcShape, SrcAccessor> const & source, pair<DestIterator, DestAccessor> const & dest, const ConvolutionOptions<N> & opt); }
Usage:
#include <vigra/multi_convolution.hxx>
MultiArray<3, unsigned char>::size_type shape(width, height, depth); MultiArray<3, unsigned char> source(shape); MultiArray<3, TinyVector<float, 3> > dest(shape); ... // compute gradient symmetricGradientMultiArray(srcMultiArrayRange(source), destMultiArray(dest));
Usage with anisotropic data:
#include <vigra/multi_convolution.hxx>
MultiArray<3, unsigned char>::size_type shape(width, height, depth); MultiArray<3, unsigned char> source(shape); MultiArray<3, TinyVector<float, 3> > dest(shape); TinyVector<float, 3> step_size; ... // compute gradient symmetricGradientMultiArray(srcMultiArrayRange(source), destMultiArray(dest), ConvolutionOptions<3>().stepSize(step_size));
Required Interface:
see convolveMultiArrayOneDimension(), in addition:
int dimension = 0;
VectorElementAccessor<DestAccessor> elementAccessor(0, dest);
void vigra::laplacianOfGaussianMultiArray | ( | ... | ) |
Calculate Laplacian of a N-dimensional arrays using Gaussian derivative filters.
This function computes the Laplacian the given N-dimensional array with a sequence of second-derivative-of-Gaussian filters at the given standard deviation sigma
. Both source and destination arrays are represented by iterators, shape objects and accessors. Both source and destination arrays must have scalar value_type. This function is implemented by calls to separableConvolveMultiArray() with the appropriate kernels, followed by summation.
Anisotropic data should be passed with appropriate ConvolutionOptions, the parameter opt
is otherwise optional unless the parameter sigma
is left out.
Declarations:
pass arguments explicitly:
namespace vigra { template <class SrcIterator, class SrcShape, class SrcAccessor, class DestIterator, class DestAccessor> void laplacianOfGaussianMultiArray(SrcIterator siter, SrcShape const & shape, SrcAccessor src, DestIterator diter, DestAccessor dest, double sigma, const ConvolutionOptions<N> & opt); }
use argument objects in conjunction with Argument Object Factories :
namespace vigra { template <class SrcIterator, class SrcShape, class SrcAccessor, class DestIterator, class DestAccessor> void laplacianOfGaussianMultiArray(triple<SrcIterator, SrcShape, SrcAccessor> const & source, pair<DestIterator, DestAccessor> const & dest, double sigma, const ConvolutionOptions<N> & opt); }
Usage:
#include <vigra/multi_convolution.hxx>
MultiArray<3, float> source(shape); MultiArray<3, float> laplacian(shape); ... // compute Laplacian at scale sigma laplacianOfGaussianMultiArray(srcMultiArrayRange(source), destMultiArray(laplacian), sigma);
Usage with anisotropic data:
#include <vigra/multi_convolution.hxx>
MultiArray<3, float> source(shape); MultiArray<3, float> laplacian(shape); TinyVector<float, 3> step_size; TinyVector<float, 3> resolution_sigmas; ... // compute Laplacian at scale sigma laplacianOfGaussianMultiArray(srcMultiArrayRange(source), destMultiArray(laplacian), sigma, ConvolutionOptions<3>().stepSize(step_size).resolutionStdDev(resolution_sigmas));
Required Interface:
see separableConvolveMultiArray(), in addition:
int dimension = 0;
VectorElementAccessor<DestAccessor> elementAccessor(0, dest);
void vigra::hessianOfGaussianMultiArray | ( | ... | ) |
Calculate Hessian matrix of a N-dimensional arrays using Gaussian derivative filters.
This function computes the Hessian matrix the given scalar N-dimensional array with a sequence of second-derivative-of-Gaussian filters at the given standard deviation sigma
. Both source and destination arrays are represented by iterators, shape objects and accessors. The destination array must have a vector valued element type with N*(N+1)/2 elements (it represents the upper triangular part of the symmetric Hessian matrix). This function is implemented by calls to separableConvolveMultiArray() with the appropriate kernels.
Anisotropic data should be passed with appropriate ConvolutionOptions, the parameter opt
is otherwise optional unless the parameter sigma
is left out.
Declarations:
pass arguments explicitly:
namespace vigra { template <class SrcIterator, class SrcShape, class SrcAccessor, class DestIterator, class DestAccessor> void hessianOfGaussianMultiArray(SrcIterator siter, SrcShape const & shape, SrcAccessor src, DestIterator diter, DestAccessor dest, double sigma, const ConvolutionOptions<N> & opt); }
use argument objects in conjunction with Argument Object Factories :
namespace vigra { template <class SrcIterator, class SrcShape, class SrcAccessor, class DestIterator, class DestAccessor> void hessianOfGaussianMultiArray(triple<SrcIterator, SrcShape, SrcAccessor> const & source, pair<DestIterator, DestAccessor> const & dest, double sigma, const ConvolutionOptions<N> & opt); }
Usage:
#include <vigra/multi_convolution.hxx>
MultiArray<3, float> source(shape); MultiArray<3, TinyVector<float, 6> > dest(shape); ... // compute Hessian at scale sigma hessianOfGaussianMultiArray(srcMultiArrayRange(source), destMultiArray(dest), sigma);
Usage with anisotropic data:
#include <vigra/multi_convolution.hxx>
MultiArray<3, float> source(shape); MultiArray<3, TinyVector<float, 6> > dest(shape); TinyVector<float, 3> step_size; TinyVector<float, 3> resolution_sigmas; ... // compute Hessian at scale sigma hessianOfGaussianMultiArray(srcMultiArrayRange(source), destMultiArray(dest), sigma, ConvolutionOptions<3>().stepSize(step_size).resolutionStdDev(resolution_sigmas));
Required Interface:
see separableConvolveMultiArray(), in addition:
int dimension = 0;
VectorElementAccessor<DestAccessor> elementAccessor(0, dest);
void vigra::structureTensorMultiArray | ( | ... | ) |
Calculate th structure tensor of a multi-dimensional arrays.
This function computes the gradient (outer product) tensor for each element of the given N-dimensional array with first-derivative-of-Gaussian filters at the given innerScale
, followed by Gaussian smoothing at outerScale
. Both source and destination arrays are represented by iterators, shape objects and accessors. The destination array must have a vector valued pixel type with N*(N+1)/2 elements (it represents the upper triangular part of the symmetric structure tensor matrix). If the source array is also vector valued, the resulting structure tensor is the sum of the individual tensors for each channel. This function is implemented by calls to separableConvolveMultiArray() with the appropriate kernels.
Anisotropic data should be passed with appropriate ConvolutionOptions, the parameter opt
is otherwise optional unless the parameters innerScale
and outerScale
are both left out.
Declarations:
pass arguments explicitly:
namespace vigra { template <class SrcIterator, class SrcShape, class SrcAccessor, class DestIterator, class DestAccessor> void structureTensorMultiArray(SrcIterator siter, SrcShape const & shape, SrcAccessor src, DestIterator diter, DestAccessor dest, double innerScale, double outerScale, const ConvolutionOptions<N> & opt); }
use argument objects in conjunction with Argument Object Factories :
namespace vigra { template <class SrcIterator, class SrcShape, class SrcAccessor, class DestIterator, class DestAccessor> void structureTensorMultiArray(triple<SrcIterator, SrcShape, SrcAccessor> const & source, pair<DestIterator, DestAccessor> const & dest, double innerScale, double outerScale, const ConvolutionOptions<N> & opt); }
Usage:
#include <vigra/multi_convolution.hxx>
MultiArray<3, RGBValue<float> > source(shape); MultiArray<3, TinyVector<float, 6> > dest(shape); ... // compute structure tensor at scales innerScale and outerScale structureTensorMultiArray(srcMultiArrayRange(source), destMultiArray(dest), innerScale, outerScale);
Usage with anisotropic data:
#include <vigra/multi_convolution.hxx>
MultiArray<3, RGBValue<float> > source(shape); MultiArray<3, TinyVector<float, 6> > dest(shape); TinyVector<float, 3> step_size; TinyVector<float, 3> resolution_sigmas; ... // compute structure tensor at scales innerScale and outerScale structureTensorMultiArray(srcMultiArrayRange(source), destMultiArray(dest), innerScale, outerScale, ConvolutionOptions<3>().stepSize(step_size).resolutionStdDev(resolution_sigmas));
Required Interface:
see separableConvolveMultiArray(), in addition:
int dimension = 0;
VectorElementAccessor<DestAccessor> elementAccessor(0, dest);
void vigra::convolveFFT | ( | ... | ) |
Convolve an array with a kernel by means of the Fourier transform.
Thanks to the convolution theorem of Fourier theory, a convolution in the spatial domain is equivalent to a multiplication in the frequency domain. Thus, for certain kernels (especially large, non-separable ones), it is advantageous to perform the convolution by first transforming both array and kernel to the frequency domain, multiplying the frequency representations, and transforming the result back into the spatial domain. Some kernels have a much simpler definition in the frequency domain, so that they are readily computed there directly, avoiding Fourier transformation of those kernels.
The following functions implement various variants of FFT-based convolution:
convolveFFT
, but you may provide many kernels at once (using an iterator pair specifying the kernel sequence). This has the advantage that the forward transform of the input array needs to be executed only once. convolveFFTComplex
, but you may provide many kernels at once (using an iterator pair specifying the kernel sequence). This has the advantage that the forward transform of the input array needs to be executed only once. The output arrays must have the same shape as the input arrays. In the "Many" variants of the convolution functions, the kernels must all have the same shape.
The origin of the kernel is always assumed to be in the center of the kernel array (precisely, at the point floor(kernel.shape() / 2.0)
, except when the half-space format is used, see below). The function moveDCToUpperLeft() will be called internally to align the kernel with the transformed input as appropriate.
If a real input is combined with a real kernel, the kernel is automatically assumed to be defined in the spatial domain. If a real input is combined with a complex kernel, the kernel is assumed to be defined in the Fourier domain in half-space format. If the input array is complex, a flag fourierDomainKernel
determines where the kernel is defined.
When the kernel is defined in the spatial domain, the convolution functions will automatically pad (enlarge) the input array by at least the kernel radius in each direction. The newly added space is filled according to reflective boundary conditions in order to minimize border artifacts during convolution. It is thus ensured that convolution in the Fourier domain yields the same results as convolution in the spatial domain (e.g. when separableConvolveMultiArray() is called with the same kernel). A little further padding may be added to make sure that the padded array shape uses integers which have only small prime factors, because FFTW is then able to use the fastest possible algorithms. Any padding is automatically removed from the result arrays before the function returns.
When the kernel is defined in the frequency domain, it must be complex-valued, and its shape determines the shape of the Fourier representation (i.e. the input is padded according to the shape of the kernel). If we are going to perform a complex-valued convolution, the kernel must be defined for the entire frequency domain, and its shape directly determines the size of the FFT.
In contrast, a frequency domain kernel for a real-valued convolution must have symmetry properties that allow to drop half of the kernel coefficients, as in the R2C transform. That is, the kernel must have the half-space format, that is the shape returned by fftwCorrespondingShapeR2C(fourier_shape)
, where fourier_shape
is the desired logical shape of the frequency representation (and thus the size of the padded input). The origin of the kernel must be at the point (0, floor(fourier_shape[0] / 2.0), ..., floor(fourier_shape[N-1] / 2.0))
(i.e. as in a regular kernel except for the first dimension).
The Real
type in the declarations can be double
, float
, and long double
. Your program must always link against libfftw3
. If you use float
or long double
arrays, you must additionally link against libfftw3f
and libfftw3l
respectively.
The Fourier transform functions internally create FFTW plans which control the algorithm details. The plans are creates with the flag FFTW_ESTIMATE
, i.e. optimal settings are guessed or read from saved "wisdom" files. If you need more control over planning, you can use the class FFTWConvolvePlan.
See also applyFourierFilter() for corresponding functionality on the basis of the old image iterator interface.
Declarations:
Real-valued convolution with kernel in the spatial domain:
namespace vigra { template <unsigned int N, class Real, class C1, class C2, class C3> void convolveFFT(MultiArrayView<N, Real, C1> in, MultiArrayView<N, Real, C2> kernel, MultiArrayView<N, Real, C3> out); }
Real-valued convolution with kernel in the Fourier domain (half-space format):
namespace vigra { template <unsigned int N, class Real, class C1, class C2, class C3> void convolveFFT(MultiArrayView<N, Real, C1> in, MultiArrayView<N, FFTWComplex<Real>, C2> kernel, MultiArrayView<N, Real, C3> out); }
Series of real-valued convolutions with kernels in the spatial or Fourier domain (the kernel and out sequences must have the same length):
namespace vigra { template <unsigned int N, class Real, class C1, class KernelIterator, class OutIterator> void convolveFFTMany(MultiArrayView<N, Real, C1> in, KernelIterator kernels, KernelIterator kernelsEnd, OutIterator outs); }
Complex-valued convolution (parameter fourierDomainKernel
determines if the kernel is defined in the spatial or Fourier domain):
namespace vigra { template <unsigned int N, class Real, class C1, class C2, class C3> void convolveFFTComplex(MultiArrayView<N, FFTWComplex<Real>, C1> in, MultiArrayView<N, FFTWComplex<Real>, C2> kernel, MultiArrayView<N, FFTWComplex<Real>, C3> out, bool fourierDomainKernel); }
Series of complex-valued convolutions (parameter fourierDomainKernel
determines if the kernels are defined in the spatial or Fourier domain, the kernel and out sequences must have the same length):
namespace vigra { template <unsigned int N, class Real, class C1, class KernelIterator, class OutIterator> void convolveFFTComplexMany(MultiArrayView<N, FFTWComplex<Real>, C1> in, KernelIterator kernels, KernelIterator kernelsEnd, OutIterator outs, bool fourierDomainKernel); }
Usage:
#include <vigra/multi_fft.hxx>
Namespace: vigra
// convolve real array with a Gaussian (sigma=1) defined in the spatial domain // (implicitly uses padding by at least 4 pixels) MultiArray<2, double> src(Shape2(w, h)), dest(Shape2(w,h)); MultiArray<2, double> spatial_kernel(Shape2(9, 9)); Gaussian<double> gauss(1.0); for(int y=0; y<9; ++y) for(int x=0; x<9; ++x) spatial_kernel(x, y) = gauss(x-4.0)*gauss(y-4.0); convolveFFT(src, spatial_kernel, dest); // convolve real array with a Gaussian (sigma=1) defined in the Fourier domain // (uses no padding, because the kernel size corresponds to the input size) MultiArray<2, FFTWComplex<double> > fourier_kernel(fftwCorrespondingShapeR2C(src.shape())); int y0 = h / 2; for(int y=0; y<fourier_kernel.shape(1); ++y) for(int x=0; x<fourier_kernel.shape(0); ++x) fourier_kernel(x, y) = exp(-0.5*sq(x / double(w))) * exp(-0.5*sq((y-y0)/double(h))); convolveFFT(src, fourier_kernel, dest);
void vigra::convolveFFTComplex | ( | ... | ) |
Convolve a complex-valued array by means of the Fourier transform.
See convolveFFT() for details.
void vigra::convolveFFTMany | ( | ... | ) |
Convolve a real-valued array with a sequence of kernels by means of the Fourier transform.
See convolveFFT() for details.
void vigra::convolveFFTComplexMany | ( | ... | ) |
Convolve a complex-valued array with a sequence of kernels by means of the Fourier transform.
See convolveFFT() for details.
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