HoughCircles

Search for circles using the Hough transform.
Can use available TwinCAT Job Tasks for executing parallel code regions.
Can return partial results when canceled by Watchdog.

Syntax

Definition:

HRESULT HoughCircles(
    HRESULT          hrPrev,
    ITcVnImage*      ipSrcImage,
    ITcVnContainer*& ipCircles,
    double           fInvAccuRatio,
    double           fMinDist,
    ETcVnHoughMethod eHoughMethod = HM_GRADIENT,
    double           fParam1 = 100,
    double           fParam2 = 100,
    ULONG            nMinRadius = 0,
    ULONG            nMaxRadius = 0
)

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 (USINT, 1 channel, gray-level)
ipCircles	ITcVnContainer*&		Returns a container which is filled with the found circles (ContainerType_Vector_TcVnVector3_REAL; Each container element contains the x coordinate of the circle center [0], the y coordinate of the circle center [1], and the radius [2], respectively. Non-zero interface pointers are reused.)
fInvAccuRatio	double		Inverted ratio of the accumulator size in relation to the source image's size (must be > 0. A value of 2 means that the size is halved in both directions.)
fMinDist	double		Smallest allowed distance of two circles (must be > 0)
eHoughMethod	ETcVnHoughMethod	HM_GRADIENT	Hough method to use (GRADIENT or GRADIENT_ALT)
fParam1	double	100	First method specific parameter (GRADIENT, GRADIENT_ALT: upper threshold for canny edge detection, which must be > 0)
fParam2	double	100	Second method specific parameter (GRADIENT: accumulator threshold for detecting circle centers, which must be > 0. GRADIENT_ALT: required circle perfectness, which must be > 0 and < 1, 1 would be a perfect circle)
nMinRadius	ULONG	0	Minimum circle radius allowed
nMaxRadius	ULONG	0	Maximum circle radius allowed (if 0, the value is internally set to max(image rows, image columns))

Return value

HRESULT

Required License

TC3 Vision Base

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