Distance transform: Gwyddion Library Reference Manual

Distance transform

Distance transform — Distance transform and related morphological operations

Functions

const GwyEnum *	gwy_distance_transform_type_get_enum ()
void	gwy_nield_distance_transform ()
void	gwy_nield_shrink ()
void	gwy_nield_grow ()
void	gwy_nield_thin ()

Types and Values

enum	GwyDistanceTransformType

Includes

#include <libgwyddion/gwyddion.h>

Description

Functions

gwy_distance_transform_type_get_enum()

const GwyEnum *
gwy_distance_transform_type_get_enum (void);

Returns GwyEnum for GwyDistanceTransformType enum type.

Returns

NULL-terminated GwyEnum which must not be modified nor freed.

gwy_nield_distance_transform()

void
gwy_nield_distance_transform (GwyNield *nield,
                              GwyField *distances,
                              GwyDistanceTransformType dtype,
                              gboolean merged,
                              gboolean from_border);

Performs a distance transform of a number field.

For each non-zero value, a distance to the grain boundary is calculated, measured in pixels. For unmarked pixels in nield , the distance is set to zero.

If merged is TRUE, there is no boundary between touching grains. The distance is calculated from unmarked area (and possibly from image edges). If merged is TRUE, regions filled with different numbers in nield are considered individually, creating boundaries also where different grains touch.

If the entire nield is marked, from_border is FALSE and either merged is TRUE or nield is filled with the same value, there are no boundaries to calculate the distance from. In such case distances is filled with a huge positive value (like G_MAXDOUBLE).

Parameters

nield	A number field with zeros in empty space and nonzeros in marked areas.
distances	Output data field which will be resized and filled with the distances.
dtype	Type of simple distance to use.
merged	`TRUE` to only distinguish marked/unmarked; `FALSE` to distinuish grain numbers.
from_border	`TRUE` to consider image edges to be grain boundaries.

gwy_nield_shrink()

void
gwy_nield_shrink (GwyNield *nield,
                  gdouble amount,
                  GwyDistanceTransformType dtype,
                  gboolean merged,
                  gboolean from_border);

Erodes a number field containing mask by specified amount using a distance measure.

Non-zero pixels in nield will be replaced with zeros if they are not farther than amount from the grain boundary as defined by dtype .

Parameters

nield	A number field with zeros in empty space and nonzeros in grains.
amount	How much the grains should be reduced, in pixels. It is inclusive, i.e. pixels that are `amount` far from the border will be removed.
dtype	Type of simple distance to use.
merged	`TRUE` to only distinguish marked/unmarked; `FALSE` to distinuish grain numbers.
from_border	`TRUE` to consider image edges to be grain boundaries. `FALSE` to reduce grains touching field boundaries only along the boundaries.

gwy_nield_grow()

void
gwy_nield_grow (GwyNield *nield,
                gdouble amount,
                GwyDistanceTransformType dtype,
                gboolean prevent_touching);

Dilates a number field containing mask by specified amount using a distance measure.

Non-positive pixels in field will be replaced with ones if they are not farther than amount from the grain boundary as defined by dtype .

Parameters

nield	A number field with zeros in empty space and nonzeros in grains.
amount	How much the grains should be expanded, in pixels. It is inclusive, i.e. exterior pixels that are `amount` far from the border will be filled.
dtype	Type of simple distance to use.
prevent_touching	`TRUE` to prevent grain touching, i.e. the growth stops where two grains would touch. `FALSE` to simply expand the grains, without regard to grain connectivity.

gwy_nield_thin()

void
gwy_nield_thin (GwyNield *nield);

Performs thinning of a data field containing mask.

The result of thinning is a ‘skeleton’ mask consisting of single-pixel thin lines.

Parameters

nield

A number field with zeros in empty space and nonzeros in grains.

Types and Values

enum GwyDistanceTransformType

Type of distance transform.

Members

GWY_DISTANCE_TRANSFORM_CITYBLOCK	City-block distance (sum of horizontal and vertical distances).
GWY_DISTANCE_TRANSFORM_CONN4	Four-connectivity distance; another name for city-block distance.
GWY_DISTANCE_TRANSFORM_CHESS	Chessboard distance (maximum of horizontal and vertical distance).
GWY_DISTANCE_TRANSFORM_CONN8	Eight-connectivity distance; another name for chessboard distance.
GWY_DISTANCE_TRANSFORM_OCTAGONAL48	Octagonal distance beginning from city-block.
GWY_DISTANCE_TRANSFORM_OCTAGONAL84	Octagonal distance beginning from chess.
GWY_DISTANCE_TRANSFORM_OCTAGONAL	Average octagonal distance, i.e. the mean of the 48 and 84 distances.
GWY_DISTANCE_TRANSFORM_EUCLIDEAN	True Euclidean distance.