F_VN_AdjustSearchWindowOrientationToLinearEdge

Adjust the search window to be orthogonal to a linear edge. Might be helpful before calling edge localization and distance measurement functions that rely on the search window.
Can use available TwinCAT Job Tasks for executing parallel code regions.

Syntax

Definition:

FUNCTION F_VN_AdjustSearchWindowOrientationToLinearEdge : HRESULT
VAR_INPUT
    ipSrcImage     : ITcVnImage;
END_VAR
VAR_IN_OUT
    aStartPoint    : TcVnPoint2_REAL;
    aEndPoint      : TcVnPoint2_REAL;
END_VAR
VAR_INPUT
    eEdgeDirection : ETcVnEdgeDirection;
    fMinStrength   : REAL;
    nMaxThickness  : UDINT;
    nSearchLines   : UDINT;
    hrPrev         : HRESULT;
END_VAR

Inputs

Name	Type	Description
ipSrcImage	ITcVnImage	Source image
eEdgeDirection	ETcVnEdgeDirection	Specification of the edge direction to search for
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
nSearchLines	UDINT	Width of the search window, i.e. the number of search lines (3, 5, 7, ...), centered around the line specified by aStartPoint and aEndPoint
hrPrev	HRESULT	HRESULT indicating the result of previous operations (If SUCCEEDED(hrPrev) equals false, no operation is executed.)

In/Outputs

Name	Type	Description
aStartPoint	TcVnPoint2_REAL	Position from which to start the search process (in the direction of aEndPoint), which is not changed
aEndPoint	TcVnPoint2_REAL	Position where the search process ends, which is adjusted by this function

Return value

HRESULT

Further information

The F_VN_AdjustSearchWindowOrientationToLinearEdge function rotates the search field for measurement functions in such a way that it lies orthogonal to a linear edge.

Parameter

Input image

The ipSrcImage input image must contain an edge in accordance with the parameters for edge detection.

Search window ^{(Return value)}

The search window to be adjusted is transferred as a reference so that it can be changed by the function. The search window consists of the central search line, which is indicated by a aStartPoint start point and aEndPoint end point, as well as the number of nSearchLines search lines.

Following the function call, aStartPoint and aEndPoint contain the adjusted central search line. This is now orthogonal to the linear edge on the ipSrcImage input image.

Parameters for edge localization

The remaining parameters are explained in detail in the chapter Edge localization.

Application

The adaptation of the search window to an edge looks like this, for example:

hr := F_VN_(
    ipSrcImage      := ipImageIn,
    aStartPoint     := aStartPoint,
    aEndPoint       := aEndPoint,
    eEdgeDirection  := eDirection,
    fMinStrength    := fMinStrength,
    nMaxThickness   := nMaxThickness,
    nSearchLines    := nSearchLines,
    hrPrev          := hr);

Required License

TC3 Vision Metrology 2D