LocateEllipse

Locate an ellipse.
Can use available TwinCAT Job Tasks for executing parallel code regions.
Can return partial results when canceled by Watchdog.

Syntax

Definition:

HRESULT LocateEllipse(
    HRESULT                     hrPrev,
    ITcVnImage*                 ipSrcImage,
    TcVnRotatedRectangle&       stEllipse,
    TcVnPoint2_REAL&            aCenter,
    float                       fSearchRadius,
    ETcVnEdgeDirection          eEdgeDirection,
    float                       fMinStrength,
    ULONG                       nMaxThickness = 10,
    bool                        bInvertSearchDirection = false,
    float                       fMinSearchRadius = 0,
    ULONG                       nSubpixelsIterations = 10,
    ULONG                       nSearchLines = 92,
    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)

stEllipse

TcVnRotatedRectangle&

 

Returns the detected ellipse

aCenter

TcVnPoint2_REAL&

 

The expected ellipse center

fSearchRadius

float

 

Radius around aCenter to search for edges

eEdgeDirection

ETcVnEdgeDirection

 

Specification of the edge direction to search for (from center to outside ellipse or other way round, if bInvertSearchDirection is true)

fMinStrength

float

 

Specification of the minimum strength (intensity difference) of the edge to search for

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 ellipse in direction of the center

fMinSearchRadius

float

0

Radius around aCenter to skip before starting to search for edges (e.g. to save time or if the center contains edges that should be ignored)

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)

nSearchLines

ULONG

92

Specifies the amount of search lines, which are equally distributed in all directions (must be >= 8 and a multiple of 4)

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 ellipse contour (optional, set to 0 if not required; ContainerType_Vector_TcVnPoint2_REAL; Non-zero interface pointers are reused.)

LocateEllipse 1: Return value

HRESULT

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