F_VN_DetectPatternPointsExp

F_VN_DetectPatternPointsExp 1:

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

Syntax

Definition:

FUNCTION F_VN_DetectPatternPointsExp : HRESULT
VAR_INPUT
    ipSrcImage            : ITcVnImage;
    ipPatternPoints       : Reference To ITcVnContainer;
END_VAR
VAR_IN_OUT
    stBlobDetectionParams : TcVnParamsBlobDetection;
END_VAR
VAR_INPUT
    nNumberOfPoints       : UDINT;
    fSizeDiffThresFactor  : REAL;
    bSubpixelAccuracy     : BOOL;
    eEdgeDirection        : ETcVnEdgeDirection;
    fMinStrength          : REAL;
    nMaxThickness         : UDINT;
    nSubpixelsIterations  : UDINT;
    nSearchLines          : UDINT;
    fApproxPrecision      : REAL;
    eAlgorithm            : ETcVnEdgeDetectionAlgorithm;
    hrPrev                : HRESULT;
END_VAR

F_VN_DetectPatternPointsExp 2: Inputs

Name

Type

Description

ipSrcImage

ITcVnImage

Source image (USINT, 1 channel)

ipPatternPoints

Reference To ITcVnContainer

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

nNumberOfPoints

UDINT

Expected number of pattern points

fSizeDiffThresFactor

REAL

Threshold for filtering contours by average size

bSubpixelAccuracy

BOOL

If true, the pattern points are detected with subpixel accuracy

eEdgeDirection

ETcVnEdgeDirection

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

fMinStrength

REAL

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

nMaxThickness

UDINT

Specification of the maximum thickness of the edge to search for, which means fMinStrength must be reached within nMaxThickness pixels

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)

nSearchLines

UDINT

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

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

hrPrev

HRESULT

HRESULT indicating the result of previous operations (If SUCCEEDED(hrPrev) equals false, no operation is executed.)

F_VN_DetectPatternPointsExp 3: In/Outputs

Name

Type

Description

stBlobDetectionParams

TcVnParamsBlobDetection

Parameters to detect and filter contours.

F_VN_DetectPatternPointsExp 4: 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