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Kernel2D< ARITHTYPE > | ![]() |
Generic 2 dimensional convolution kernel. More...
#include <vigra/stdconvolution.hxx>
Public Types | |
typedef BasicImage< value_type > ::Accessor | Accessor |
typedef BasicImage< value_type > ::ConstAccessor | ConstAccessor |
typedef BasicImage< value_type > ::const_traverser | ConstIterator |
typedef BasicImage< value_type > ::traverser | Iterator |
typedef ARITHTYPE | value_type |
Public Member Functions | |
ConstAccessor | accessor () const |
Accessor | accessor () |
BorderTreatmentMode | borderTreatment () const |
ConstIterator | center () const |
Iterator | center () |
int | height () const |
void | initDisk (int radius) |
Kernel2D & | initExplicitly (Diff2D upperleft, Diff2D lowerright) |
template<class KernelIterator > | |
void | initSeparable (KernelIterator kxcenter, int xleft, int xright, KernelIterator kycenter, int yleft, int yright) |
void | initSeparable (Kernel1D< value_type > &kx, Kernel1D< value_type > &ky) |
Kernel2D (Kernel2D const &k) | |
Kernel2D () | |
Point2D | lowerRight () const |
value_type | norm () const |
void | normalize () |
void | normalize (value_type norm) |
value_type | operator() (int x, int y) const |
value_type & | operator() (int x, int y) |
InitProxy | operator= (value_type const &v) |
Kernel2D & | operator= (Kernel2D const &k) |
value_type | operator[] (Diff2D const &d) const |
value_type & | operator[] (Diff2D const &d) |
void | setBorderTreatment (BorderTreatmentMode new_mode) |
Point2D | upperLeft () const |
int | width () const |
~Kernel2D () |
Generic 2 dimensional convolution kernel.
This kernel may be used for convolution of 2 dimensional signals.
Convolution functions access the kernel via an ImageIterator which they get by calling center(). This iterator points to the center of the kernel. The kernel's size is given by its upperLeft() (upperLeft().x <= 0, upperLeft().y <= 0) and lowerRight() (lowerRight().x >= 0, lowerRight().y >= 0) methods. The desired border treatment mode is returned by borderTreatment(). (Note that the 2D convolution functions don't currently support all modes.)
The different init functions create a kernel with the specified properties. The requirements for the kernel's value_type depend on the init function used. At least NumericTraits must be defined.
The kernel defines a factory function kernel2d() to create an argument object (see Kernel Argument Object Factories).
Usage:
#include <vigra/stdconvolution.hxx>
Namespace: vigra
vigra::FImage src(w,h), dest(w,h); ... // define horizontal Sobel filter vigra::Kernel2D<float> sobel; sobel.initExplicitly(Diff2D(-1,-1), Diff2D(1,1)) = // upper left and lower right 0.125, 0.0, -0.125, 0.25, 0.0, -0.25, 0.125, 0.0, -0.125; vigra::convolveImage(srcImageRange(src), destImage(dest), kernel2d(sobel));
Required Interface:
value_type v = NumericTraits<value_type>::one();
See also the init functions.
typedef ARITHTYPE value_type |
the kernel's value type
typedef BasicImage<value_type>::traverser Iterator |
2D random access iterator over the kernel's values
typedef BasicImage<value_type>::const_traverser ConstIterator |
const 2D random access iterator over the kernel's values
typedef BasicImage<value_type>::Accessor Accessor |
the kernel's accessor
typedef BasicImage<value_type>::ConstAccessor ConstAccessor |
the kernel's const accessor
Kernel2D | ( | ) |
Default constructor. Creates a kernel of size 1x1 which would copy the signal unchanged.
~Kernel2D | ( | ) |
Destructor.
InitProxy operator= | ( | value_type const & | v | ) |
Initialization. This initializes the kernel with the given constant. The norm becomes v*width()*height().
Instead of a single value an initializer list of length width()*height() can be used like this:
vigra::Kernel2D<float> binom; binom.initExplicitly(Diff2D(-1,-1), Diff2D(1,1)) = 0.0625, 0.125, 0.0625, 0.125, 0.25, 0.125, 0.0625, 0.125, 0.0625;
In this case, the norm will be set to the sum of the init values. An initializer list of wrong length will result in a run-time error.
void initSeparable | ( | Kernel1D< value_type > & | kx, | |
Kernel1D< value_type > & | ky | |||
) |
Init the 2D kernel as the cartesian product of two 1D kernels of type Kernel1D. The norm becomes the product of the two original norms.
Required Interface:
The kernel's value_type must be a linear algebra.
vigra::Kernel2D<...>::value_type v; v = v * v;
void initSeparable | ( | KernelIterator | kxcenter, | |
int | xleft, | |||
int | xright, | |||
KernelIterator | kycenter, | |||
int | yleft, | |||
int | yright | |||
) |
Init the 2D kernel as the cartesian product of two 1D kernels given explicitly by iterators and sizes. The norm becomes the sum of the resulting kernel values.
Required Interface:
The kernel's value_type must be a linear algebra.
vigra::Kernel2D<...>::value_type v; v = v * v; v += v;
Preconditions:
xleft <= 0; xright >= 0; yleft <= 0; yright >= 0;
void initDisk | ( | int | radius | ) |
Init the 2D kernel as a circular averaging filter. The norm will be calculated as NumericTraits<value_type>::one() / (number of non-zero kernel values)
. The kernel's value_type must be a linear space.
Required Interface:
value_type v = vigra::NumericTraits<value_type>::one(); double d; v = d * v;
Precondition:
radius > 0;
Init the kernel by an explicit initializer list. The upper left and lower right corners of the kernel must be passed. A comma-separated initializer list is given after the assignment operator. This function is used like this:
// define horizontal Sobel filter vigra::Kernel2D<float> sobel; sobel.initExplicitly(Diff2D(-1,-1), Diff2D(1,1)) = 0.125, 0.0, -0.125, 0.25, 0.0, -0.25, 0.125, 0.0, -0.125;
The norm is set to the sum of the initialzer values. If the wrong number of values is given, a run-time error results. It is, however, possible to give just one initializer. This creates an averaging filter with the given constant:
vigra::Kernel2D<float> average3x3; average3x3.initExplicitly(Diff2D(-1,-1), Diff2D(1,1)) = 1.0/9.0;
Here, the norm is set to value*width()*height().
Preconditions:
1. upperleft.x <= 0; 2. upperleft.y <= 0; 3. lowerright.x >= 0; 4. lowerright.y >= 0; 5. the number of values in the initializer list is 1 or equals the size of the kernel.
Point2D upperLeft | ( | ) | const |
Coordinates of the upper left corner of the kernel.
Point2D lowerRight | ( | ) | const |
Coordinates of the lower right corner of the kernel.
int width | ( | ) | const |
Width of the kernel.
int height | ( | ) | const |
Height of the kernel.
Iterator center | ( | ) |
ImageIterator that points to the center of the kernel (coordinate (0,0)).
ConstIterator center | ( | ) | const |
ImageIterator that points to the center of the kernel (coordinate (0,0)).
value_type& operator() | ( | int | x, | |
int | y | |||
) |
Access kernel entry at given position.
value_type operator() | ( | int | x, | |
int | y | |||
) | const |
Read kernel entry at given position.
value_type& operator[] | ( | Diff2D const & | d | ) |
Access kernel entry at given position.
value_type operator[] | ( | Diff2D const & | d | ) | const |
Read kernel entry at given position.
value_type norm | ( | ) | const |
Norm of the kernel (i.e. sum of its elements).
Accessor accessor | ( | ) |
The kernels default accessor.
ConstAccessor accessor | ( | ) | const |
The kernels default const accessor.
void normalize | ( | value_type | norm | ) |
Normalize the kernel to the given value. (The norm is the sum of all kernel elements.) The kernel's value_type must be a division algebra or algebraic field.
Required Interface:
value_type v = vigra::NumericTraits<value_type>::one(); // if norm is not // given explicitly v += v; v = v * v; v = v / v;
void normalize | ( | ) |
Normalize the kernel to norm 1.
BorderTreatmentMode borderTreatment | ( | ) | const |
current border treatment mode
void setBorderTreatment | ( | BorderTreatmentMode | new_mode | ) |
Set border treatment mode. Only BORDER_TREATMENT_CLIP
and BORDER_TREATMENT_AVOID
are currently allowed.
© Ullrich Köthe (ullrich.koethe@iwr.uni-heidelberg.de) |
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