F_VN_MeasureEdgeDistanceExp

Syntax

Definition:

FUNCTION F_VN_MeasureEdgeDistanceExp : HRESULT
VAR_INPUT
    ipSrcImage             : ITcVnImage;
END_VAR
VAR_IN_OUT
    fAvgDistance           : REAL;
    aStartPoint            : TcVnPoint2_REAL;
    aEndPoint              : TcVnPoint2_REAL;
END_VAR
VAR_INPUT
    eEdgeDirection         : ETcVnEdgeDirection;
    fMinStrength           : REAL;
    nSearchLines           : UDINT;
    fSearchLineDist        : REAL;
    nMaxThickness          : UDINT;
    bInvertSearchDirection : BOOL;
    fSearchGap             : REAL;
    nSubpixelsIterations   : UDINT;
    fApproxPrecision       : REAL;
    eAlgorithm             : ETcVnEdgeDetectionAlgorithm;
    ipEdgePoints1          : Reference To  ITcVnContainer;
    ipEdgePoints2          : Reference To  ITcVnContainer;
    ipDistances            : Reference To  ITcVnContainer;
    hrPrev                 : HRESULT;
END_VAR

Inputs

Name	Type	Description
ipSrcImage	ITcVnImage	Source image (1 channel)
eEdgeDirection	ETcVnEdgeDirection	Specification of the edge direction from aStartPoint to aEndPoint to search for
fMinStrength	REAL	Specification of the minimum strength (intensity difference) of the edge to search for
nSearchLines	UDINT	Width of the search window, i.e. the number of search lines (1, 3, 5, 7, ...), centered around the line specified by aStartPoint and aEndPoint
fSearchLineDist	REAL	Distance between the search lines in pixels (> 0)
nMaxThickness	UDINT	Specification of the maximum thickness of the edge to search for, which means fMinStrength must be reached within nMaxThickness pixels
bInvertSearchDirection	BOOL	If true, the search starts from the center point between aStartPoint and aEndPoint in both directions
fSearchGap	REAL	Optional width of a gap (>= 0, centered between aStartPoint and aEndPoint), that is neglected for searching edges (can reduce execution time). The 2 edges to search for must be on different sides of the gap.
nSubpixelsIterations	UDINT	Specifies the number of subpixels (for INTERPOLATION, 10 - 20 usually is sufficient) or maximum number of iterations for optimizing the parameters (for APPROX_ERF and APPROX_GAUSSIAN, 50 - 100 usually is sufficient)
fApproxPrecision	REAL	Specifies the approximation precision for APPROX_ERF and APPROX_GAUSSIAN (0.001 usually is sufficient, unused for INTERPOLATION)
eAlgorithm	ETcVnEdgeDetectionAlgorithm	Selection of the edge detection algorithm
ipEdgePoints1	Reference To ITcVnContainer	Returns the detected edge points of the edge near aStartPoint (optional, set to 0 if not required; ContainerType_Vector_TcVnPoint2_REAL)
ipEdgePoints2	Reference To ITcVnContainer	Returns the detected edge points of the edge near aEndPoint (optional, set to 0 if not required; ContainerType_Vector_TcVnPoint2_REAL)
ipDistances	Reference To ITcVnContainer	Returns the distances between the detected edge points (optional, set to 0 if not required; ContainerType_Vector_REAL)
hrPrev	HRESULT	HRESULT indicating the result of previous operations (If SUCCEEDED(hrPrev) equals false, no operation is executed.)

In/Outputs

Name	Type	Description
fAvgDistance	REAL	Returns the average distance between the detected edges
aStartPoint	TcVnPoint2_REAL	Position from which to start the search process (in the direction of aEndPoint)
aEndPoint	TcVnPoint2_REAL	Position where the search process ends

Return value

HRESULT

Weiterführende Informationen

Die Funktion F_VN_MeasureEdgeDistanceExp ist die Expert-Variante von F_VN_MeasureEdgeDistance. Sie enthält zusätzliche Parameter.

Parameter

Eingangsbild

Das Eingangsbild ipSrcImage muss ein 1-kanaliges Grauwertbild sein.

Minimaler Abstand ^{(Rückgabewert)}

Der Parameter fAvgDistance gibt des minimalen Abstand der beiden lokalisierten Kanten zurück.

Lokalisierte Kantenpunkte ^{(Expert, Rückgabewert)}

Die Container ipEdgePoints1 und ipEdgePoints2 geben die exakten Punkte zurück, die anhand jeder Suchlinie lokalisiert wurden. Falls nicht benötigt, kann anstatt eines Interface Pointers der Wert 0 übergeben werden.

Gemessene Abstände ^{(Expert, Rückgabewert)}

Der Container ipDistances gibt alle gemessenen Abstände zwischen gegenüberliegenden Punkten zurück. Falls nicht benötigt, kann anstatt eines Interface Pointers der Wert 0 übergeben werden.

Such-Lücke ^(Expert)

Bereich in der Mitte der definierten Suchlinie, der bei der Suche ausgelassen wird. Dadurch kann die Ausführungszeit verringert werden.

Parameter zur Kantenlokalisierung

Die restlichen Parameter sind ausführlich im Kapitel Kantenlokalisierung erklärt.

Anwendung

Die Vermessung einer Kantendistanz mit Expert-Parametern sieht z. B. so aus:

hr := F_VN_MeasureEdgeDistance(
    ipSrcImage              :=   ipImageIn, 
    fAvgDistance            :=   fDistance
    aStartPoint             :=   aStartPoint, 
    aEndPoint               :=   aEndPoint,
    eEdgeDirection          :=   TCVN_ED_LIGHT_TO_DARK,
    fMinStrength            :=   fMinStrength, 
    nSearchLines            :=   nSearchLines,
    fSearchLineDist         :=  3
    nMaxThickness           :=  7,
    bInvertSearchDirection  :=  TRUE,
    nSubpixelsIterations    :=  nSubpixIter,
    fApproxPrecision        :=  0.0001,
    eAlgorithm              :=  eAlgorithm,
    ipEdgePoints1           :=  ipEdge1, 
    ipEdgePoints2           :=  ipEdge2, 
    ipDistances             :=  ipDistances,
    hrPrev                 :=   hr
);

Die lokalisierten Kantenpunkte können mit der Funktion F_VN_DrawContours visualisiert werden:

hr := F_VN_DrawContours(ipEdgePoints1, -1, ipImageRes, aColorGreen, 5, hr);
hr := F_VN_DrawContours(ipEdgePoints2, -1, ipImageRes, aColorGreen, 5, hr);

Required License

TC3 Vision Metrology 2D

System Requirements

Development environment	Target platform	PLC libraries to include
TwinCAT V3.1.4024.54 or later	PC or CX (x64) with PL50, e.g. Intel 4-core Atom CPU	Tc3_Vision