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| Kernel2D Class Template Reference |
--- | --- | ---

Generic 2 dimensional convolution kernel. More...

`#include "vigra/stdconvolution.hxx"`

## Public Types
typedef ARITHTYPE | value_type
typedef BasicImage< value_type >::traverser | Iterator
typedef BasicImage< value_type >::const_traverser | ConstIterator
typedef BasicImage< value_type >::Accessor | Accessor
typedef BasicImage< value_type >::ConstAccessor | ConstAccessor
## Public Methods
| Kernel2D ()
| Kernel2D (Kernel2D const &k)
Kernel2D & | operator= (Kernel2D const &k)
InitProxy | operator= (value_type const &v)
| ~Kernel2D ()
void | initSeparable (Kernel1D< value_type > &kx, Kernel1D< value_type > &ky)
template<class KernelIterator> void | initSeparable (KernelIterator kxcenter, int xleft, int xright, KernelIterator kycenter, int yleft, int yright)
void | initDisk (int radius)
Kernel2D & | initExplicitly (Diff2D upperleft, Diff2D lowerright)
Point2D | upperLeft () const
Point2D | lowerRight () const
int | width () const
int | height () const
Iterator | center ()
ConstIterator | center () const
value_type & | operator() (int x, int y)
value_type | operator() (int x, int y) const
value_type & | operator[] (Diff2D const &d)
value_type | operator[] (Diff2D const &d) const
value_type | norm () const
Accessor | accessor ()
ConstAccessor | accessor () const
void | normalize (value_type norm)
void | normalize ()
BorderTreatmentMode | borderTreatment () const
void | setBorderTreatment (BorderTreatmentMode new_mode)

## Detailed Description

### template<class ARITHTYPE>
class vigra::Kernel2D< ARITHTYPE >

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.

## Member Typedef Documentation

typedef BasicImage<value_type>::Accessor Accessor

| the kernel's accessor

typedef BasicImage<value_type>::ConstAccessor ConstAccessor

| the kernel's const accessor

typedef BasicImage<value_type>::const_traverser ConstIterator

| const 2D random access iterator over the kernel's values

typedef BasicImage<value_type>::traverser Iterator

| 2D random access iterator over the kernel's values

typedef ARITHTYPE value_type

| the kernel's value type

## Constructor & Destructor Documentation

Kernel2D | ( |  | ) | `[inline]`

| Default constructor. Creates a kernel of size 1x1 which would copy the signal unchanged.

Kernel2D | ( | Kernel2D< ARITHTYPE > const & | k | ) | `[inline]`

| Copy constructor.

~Kernel2D | ( |  | ) | `[inline]`

| Destructor.

## Member Function Documentation

ConstAccessor accessor | ( |  | ) | const`[inline]`

| The kernels default const accessor.

Accessor accessor | ( |  | ) | `[inline]`

| The kernels default accessor.

BorderTreatmentMode borderTreatment | ( |  | ) | const`[inline]`

| current border treatment mode

ConstIterator center | ( |  | ) | const`[inline]`

| ImageIterator that points to the center of the kernel (coordinate (0,0)).

Iterator center | ( |  | ) | `[inline]`

| ImageIterator that points to the center of the kernel (coordinate (0,0)).

int height | ( |  | ) | const`[inline]`

| Height of the kernel.

void initDisk | ( | int | radius | ) | `[inline]`

| 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;

Kernel2D& initExplicitly | ( | Diff2D | upperleft,
|  | Diff2D | lowerright
| ) | `[inline]`

| 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.

void initSeparable | ( | KernelIterator | kxcenter,
|  | int | xleft,
|  | int | xright,
|  | KernelIterator | kycenter,
|  | int | yleft,
|  | int | yright
| ) | `[inline]`

| 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 initSeparable | ( | Kernel1D< value_type > & | kx,
|  | Kernel1D< value_type > & | ky
| ) | `[inline]`

| 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;

Point2D lowerRight | ( |  | ) | const`[inline]`

| Coordinates of the lower right corner of the kernel.

value_type norm | ( |  | ) | const`[inline]`

| Norm of the kernel (i.e. sum of its elements).

void normalize | ( |  | ) | `[inline]`

| Normalize the kernel to norm 1.

void normalize | ( | value_type | norm | ) | `[inline]`

| 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;

value_type operator() | ( | int | x,
|  | int | y
| ) | const`[inline]`

| Read kernel entry at given position.

value_type& operator() | ( | int | x,
|  | int | y
| ) | `[inline]`

| Access kernel entry at given position.

InitProxy operator= | ( | value_type const & | v | ) | `[inline]`

| 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.

Kernel2D& operator= | ( | Kernel2D< ARITHTYPE > const & | k | ) | `[inline]`

| Copy assignment.

value_type operator[] | ( | Diff2D const & | d | ) | const`[inline]`

| Read kernel entry at given position.

value_type& operator[] | ( | Diff2D const & | d | ) | `[inline]`

| Access kernel entry at given position.

void setBorderTreatment | ( | BorderTreatmentMode | new_mode | ) | `[inline]`

| Set border treatment mode. Only `BORDER_TREATMENT_CLIP` and `BORDER_TREATMENT_AVOID` are currently allowed.

Point2D upperLeft | ( |  | ) | const`[inline]`

| Coordinates of the upper left corner of the kernel.

int width | ( |  | ) | const`[inline]`

| Width of the kernel.

The documentation for this class was generated from the following file:

- vigra/stdconvolution.hxx

© Ullrich Köthe (koethe@informatik.uni-hamburg.de) Cognitive Systems Group, University of Hamburg, Germany | html generated using doxygen and Python VIGRA 1.3.2 (27 Jan 2005)