LocateCircularArc

Syntax

Definition:

HRESULT LocateCircularArc(
    HRESULT                     hrPrev,
    ITcVnImage*                 ipSrcImage,
    TcVnCircularArc&            stCircularArc,
    TcVnPoint2_REAL&            aCenter,
    float                       fSearchRadius,
    double                      fArcDirectionRad,
    ETcVnEdgeDirection          eEdgeDirection,
    float                       fMinStrength,
    double                      fAngleStepRad = 0.1,
    ULONG                       nMaxThickness = 10,
    bool                        bInvertSearchDirection = false,
    ULONG                       nSubpixelsIterations = 10,
    float                       fApproxPrecision = 0.001f,
    ETcVnEdgeDetectionAlgorithm eAlgorithm = EDA_INTERPOLATION,
    ITcVnContainer**            pipContourPoints = nullptr
)

Parameters

Name	Type	Default	Description
hrPrev	HRESULT		HRESULT indicating the result of previous operations (If SUCCEEDED(hrPrev) equals false, no operation is executed.)
ipSrcImage	ITcVnImage*		Source image (1 channel)
stCircularArc	TcVnCircularArc&		Returns the circular arc parameters
aCenter	TcVnPoint2_REAL&		Input estimated circle center (only used as a starting point to search for the circle contour, not used for the circle center estimation)
fSearchRadius	float		Input search radius (starting from aCenter, should be greater than the actual circle radius but aCenter + fSearchRadius should be within the image borders)
fArcDirectionRad	double		Input search starting direction in radian. Valid range is [-pi, +pi], where right is 0 rad, top is -pi/2 rad and bottom +pi/2 rad. The circular arc should at least be valid in range fArcDirectionRad +- 4 * fAngleStepRad)
eEdgeDirection	ETcVnEdgeDirection		Specification of the edge direction to search for
fMinStrength	float		Specification of the minimum strength (intensity difference) of the edge to search for
fAngleStepRad	double	0.1	Search step in rad (should be chosen so that about 20 - 60 steps are available for the whole arc. In most cases 0.1 rad (5.7 deg) is a good value)
nMaxThickness	ULONG	10	Specification of the maximum thickness of the edge to search for, which means fMinStrength must be reached within nMaxThickness pixels
bInvertSearchDirection	bool	false	If true, the search starts from outside the circular arc in direction of the center
nSubpixelsIterations	ULONG	10	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	float	0.001f	Specifies the approximation precision for APPROX_ERF and APPROX_GAUSSIAN (0.001 usually is sufficient, unused for INTERPOLATION)
eAlgorithm	ETcVnEdgeDetectionAlgorithm	EDA_INTERPOLATION	Selection of the edge detection algorithm
pipContourPoints	ITcVnContainer**	nullptr	Returns the subpixel accurate contour (optional, set to 0 if not required; ContainerType_Vector_TcVnPoint2_REAL; Non-zero interface pointers are reused.)

Return value

HRESULT

Required License

TC3 Vision Metrology 2D

System Requirements

Development environment	Target platform	PLC libraries to include
TwinCAT V3.1. 4024.44 or later	PC or CX (x64) with PL50, e.g. Intel 4-core Atom CPU	Tc3_Vision