LocateEdge

Locate the points of the first occuring edge inside a specified search window with subpixel accuracy.
Can use available TwinCAT Job Tasks for executing parallel code regions.
Can return partial results when canceled by Watchdog.

Syntax

Definition:

HRESULT LocateEdge(
    HRESULT                     hrPrev,
    ITcVnImage*                 ipSrcImage,
    ITcVnContainer*&            ipEdgePoints,
    TcVnPoint2_REAL&            aStartPoint,
    TcVnPoint2_REAL&            aEndPoint,
    ETcVnEdgeDirection          eEdgeDirection,
    float                       fMinStrength,
    ULONG                       nSearchLines,
    float&                      fAvgStrength,
    float                       fSearchLineDist = 1,
    ULONG                       nMaxThickness = 10,
    ULONG                       nSubpixelsIterations = 10,
    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 (1 channel)

ipEdgePoints

ITcVnContainer*&

 

Returns the detected edge points (ContainerType_Vector_TcVnPoint2_REAL)

aStartPoint

TcVnPoint2_REAL&

 

Position from which to start the search process (in the direction of aEndPoint)

aEndPoint

TcVnPoint2_REAL&

 

Position where the search process ends

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

nSearchLines

ULONG

 

Width of the search window, i.e. the number of search lines (1, 3, 5, 7, ...), centered around the line specified by aStartPoint and aEndPoint

fAvgStrength

float&

 

Returns the average strength of the detected edge

fSearchLineDist

float

1

Distance between the search lines in pixels (> 0)

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)

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

LocateEdge 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