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| NeighborCode Class Reference |
--- | --- | ---

Encapsulation of direction management for 4-neighborhood. More...

`#include "vigra/pixelneighborhood.hxx"`

## Public Types

enum | Direction { Error = -1, East = 0, North, West, South, DirectionCount, CausalFirst = North, CausalLast = West, AntiCausalFirst = South, AntiCausalLast = East }

## Static Public Methods

unsigned int | nearBorderDirectionCount (AtImageBorder b)
Direction | nearBorderDirections (AtImageBorder b, int index)
Diff2D const & | diff (Direction code)
Diff2D const & | diff (int code)
Diff2D const & | relativeDiff (Direction fromCode, Direction toCode)
Diff2D const & | relativeDiff (int fromCode, int toCode)
int | dX (Direction code)
int | dY (Direction code)
int | dX (int code)
int | dY (int code)
Direction | code (Diff2D const &diff)
bool | isDiagonal (Direction)
Diff2D const & | right ()
Diff2D const & | top ()
Diff2D const & | left ()
Diff2D const & | bottom ()
Diff2D const & | east ()
Diff2D const & | north ()
Diff2D const & | west ()
Diff2D const & | south ()

## Detailed Description

Encapsulation of direction management for 4-neighborhood.

This helper class allows the transformation between Freeman chain codes (East = 0, North = 1 etc.) and the corresponding Diff2D instances and back.

You can either use the chain codes by explicit qualification:

        // the following three lines are equivalent
        FourNeighborhood::NeighborCode::Direction d = FourNeighborhood::NeighborCode::East;
        FourNeighborCode::Direction d = FourNeighborCode::East;
        FourNeighborhood::Direction d = FourNeighborhood::East;

or you can fix 4-neighborhood by importing the entire namespace in your function:

        using namespace FourNeighborhood;

        Direction d = East;

If you want to pass 4-neighborhood codes as a template parameter, use the class FourNeighborhood::NeighborCode.

#include "vigra/pixelneighborhood.hxx"
Namespace: vigra::FourNeighborhood

## Member Enumeration Documentation

enum Direction

Freeman direction codes for the 4-neighborhood. `East = 0`, `North = 1` etc. `DirectionCount` may be used for portable loop termination conditions. `CausalFirst` and `CausalLast` are the first and last (inclusive) neighbors in the causal neighborhood, i.e. in the set of neighbors that have already been visited when the image is traversed in scan order. `AntiCausalFirst` and `AntiCausalLast` are the opposite.

Enumeration values:

  Error |
  East |
  North |
  West |
  South |
  DirectionCount |
  CausalFirst |
  CausalLast |
  AntiCausalFirst |
  AntiCausalLast |

## Member Function Documentation

Diff2D const& bottom | ( |  | ) | `[inline, static]`

| Offset to the bottom neighbor

Direction code | ( | Diff2D const & | diff | ) | `[inline, static]`

| Transform Diff2D offset into corresponding direction code. The code `Direction::Error` will be returned if `diff` is not in the 4-neighborhood.

Diff2D const& diff | ( | int | code | ) | `[inline, static]`

| Equivalent to `diff(static_cast<Direction>(code))`. (note: there is no bounds checking on the code you pass.)

Diff2D const& diff | ( | Direction | code | ) | `[inline, static]`

| Transform direction code into corresponding Diff2D offset. (note: there is no bounds checking on the code you pass.)

int dX | ( | int | code | ) | `[inline, static]`

| X-component of diff()

int dX | ( | Direction | code | ) | `[inline, static]`

| X-component of diff()

int dY | ( | int | code | ) | `[inline, static]`

| Y-component of diff()

int dY | ( | Direction | code | ) | `[inline, static]`

| Y-component of diff()

Diff2D const& east | ( |  | ) | `[inline, static]`

| Offset to the east neighbor

bool isDiagonal | ( | Direction |  | ) | `[inline, static]`

| Check whether a code refers to a diagonal direction. Useful if you want to abstract the differences between 4- and 8-neighborhood. Always `false` for 4-neighborhood.

Diff2D const& left | ( |  | ) | `[inline, static]`

| Offset to the left neighbor

unsigned int nearBorderDirectionCount | ( | AtImageBorder | b | ) | `[inline, static]`

| The number of valid neighbors if the current center is at the image border.

Direction nearBorderDirections | ( | AtImageBorder | b,
|  | int | index
| ) | `[inline, static]`

| The valid direction codes when the center is at the image border. index must be in the range `0...nearBorderDirectionCount(b)-1`.

Diff2D const& north | ( |  | ) | `[inline, static]`

| Offset to the north neighbor

Diff2D const& relativeDiff | ( | int | fromCode,
|  | int | toCode
| ) | `[inline, static]`

| Equivalent to relativeDiff(static_cast<Direction>(fromCode), static_cast<Direction>(toCode)). (note: there is no bounds checking on the code you pass.)

Diff2D const& relativeDiff | ( | Direction | fromCode,
|  | Direction | toCode
| ) | `[inline, static]`

| Get the relative offset from one neighbor to the other. For example, `relativeDiff(East, West) == Diff2D(-2,0)`. (note: there is no bounds checking on the code you pass.)

Diff2D const& right | ( |  | ) | `[inline, static]`

| Offset to the right neighbor

Diff2D const& south | ( |  | ) | `[inline, static]`

| Offset to the south neighbor

Diff2D const& top | ( |  | ) | `[inline, static]`

| Offset to the top neighbor

Diff2D const& west | ( |  | ) | `[inline, static]`

| Offset to the west neighbor

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

- vigra/pixelneighborhood.hxx

© Ullrich Köthe (koethe@informatik.uni-hamburg.de) Cognitive Systems Group, University of Hamburg, Germany | html generated using doxygen and Python VIGRA 1.4.0 (21 Dec 2005)