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| Kernel2D |

Generic 2 dimensional convolution kernel. More...

`#include <vigra/stdconvolution.hxx>`

List of all members.

## 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)
void | initGaussian (double std_dev)
void | initGaussian (double std_dev, value_type norm)
template<class KernelIterator>
void | initSeparable (KernelIterator kxcenter, int xleft, int xright, KernelIterator kycenter, int yleft, int yright)
void | initSeparable (Kernel1D< value_type > const &kx, Kernel1D< value_type > const &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 ()

## 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 | ( |  | ) |

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

Kernel2D | ( | Kernel2D< ARITHTYPE > const & | k | ) |

Copy constructor.

~Kernel2D | ( |  | ) |

Destructor.

## Member Function Documentation

ConstAccessor accessor | ( |  | ) | const

The kernels default const accessor.

Accessor accessor | ( |  | ) |

The kernels default accessor.

BorderTreatmentMode borderTreatment | ( |  | ) | const

current border treatment mode

ConstIterator center | ( |  | ) | const

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

Iterator center | ( |  | ) |

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

int height | ( |  | ) | const

Height of the kernel.

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;

Kernel2D& initExplicitly | ( | Diff2D | upperleft,
|  | Diff2D | lowerright |
| ) |  |  |

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 initGaussian | ( | double | std_dev | ) |

Init as a 2D Gaussian function with given standard deviation and unit norm.

void initGaussian | ( | double | std_dev,
|  | value_type | norm |
| ) |  |  |

Init as a 2D Gaussian function with given standard deviation and norm.

template<class KernelIterator>
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 initSeparable | ( | Kernel1D< value_type > const & | kx,
|  | Kernel1D< value_type > const & | 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;

Point2D lowerRight | ( |  | ) | const

Coordinates of the lower right corner of the kernel.

value_type norm | ( |  | ) | const

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

void normalize | ( |  | ) |

Normalize the kernel to norm 1.

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;

value_type operator() | ( | int | x,
|  | int | y |
| ) |  |  | const

Read kernel entry at given position.

value_type& operator() | ( | int | x,
|  | int | y |
| ) |  |  |

Access kernel entry at given position.

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.

Kernel2D& operator= | ( | Kernel2D< ARITHTYPE > const & | k | ) |

Copy assignment.

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

Read kernel entry at given position.

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

Access kernel entry at given position.

void setBorderTreatment | ( | BorderTreatmentMode | new_mode | ) |

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

Point2D upperLeft | ( |  | ) | const

Coordinates of the upper left corner of the kernel.

int width | ( |  | ) | const

Width of the kernel.

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

- vigra/stdconvolution.hxx

© Ullrich Köthe (ullrich.koethe@iwr.uni-heidelberg.de) Heidelberg Collaboratory for Image Processing, University of Heidelberg, Germany | html generated using doxygen and Python vigra 1.7.1 (3 Dec 2010)