DetectPatternPoints

Detects calibration pattern points (circles) within the provided image.
Can use available TwinCAT Job Tasks for executing parallel code regions.

Syntax

Definition:

HRESULT DetectPatternPoints(
    HRESULT                     hrPrev,
    ITcVnImage*                 ipSrcImage,
    ITcVnContainer*&            ipPatternPoints,
    TcVnParamsBlobDetection&    stBlobDetectionParams,
    ULONG                       nNumberOfPoints,
    float                       fSizeDiffThresFactor = 0.3f,
    bool                        bSubpixelAccuracy = false,
    ETcVnEdgeDirection          eEdgeDirection = ED_DARK_TO_LIGHT,
    float                       fMinStrength = 50,
    ULONG                       nMaxThickness = 10,
    ULONG                       nSubpixelsIterations = 10,
    ULONG                       nSearchLines = 92,
    float                       fApproxPrecision = 0.001f,
    ETcVnEdgeDetectionAlgorithm eAlgorithm = EDA_INTERPOLATION
)

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)

ipPatternPoints

ITcVnContainer*&

 

Returns the pattern point positions (ContainerType_Vector_TcVnPoint2_REAL; Non-zero interface pointers are reused.)

stBlobDetectionParams

TcVnParamsBlobDetection&

 

Parameters to detect and filter contours.

nNumberOfPoints

ULONG

 

Expected number of pattern points

fSizeDiffThresFactor

float

0.3f

Threshold for filtering contours by average size

bSubpixelAccuracy

bool

false

If true, the pattern points are detected with subpixel accuracy

eEdgeDirection

ETcVnEdgeDirection

ED_DARK_TO_LIGHT

Specification of the edge direction to search for (from center to outside circle)

fMinStrength

float

50

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

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

DetectPatternPoints 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