F_VN_MeasureAngleBetweenEdges

Measure the angle between 2 edges, using an interpolation method.
Can use available TwinCAT Job Tasks for executing parallel code regions.
Can return partial results when canceled by Watchdog.

Syntax

Definition:

FUNCTION F_VN_MeasureAngleBetweenEdges : HRESULT
VAR_INPUT
    ipSrcImage     : ITcVnImage;
END_VAR
VAR_IN_OUT
    fAngle         : REAL;
    aInnerPoint    : TcVnPoint2_REAL;
    aOuterPoint1   : TcVnPoint2_REAL;
    aOuterPoint2   : TcVnPoint2_REAL;
END_VAR
VAR_INPUT
    eEdgeDirection : ETcVnEdgeDirection;
    fMinStrength   : REAL;
    nSearchLines   : UDINT;
    hrPrev         : HRESULT;
END_VAR

Inputs

Name	Type	Description
ipSrcImage	ITcVnImage	Source image (1 channel)
eEdgeDirection	ETcVnEdgeDirection	Specification of the edge direction from aInnerPoint to aOuterPoint1 and aOuterPoint2 to search for
fMinStrength	REAL	Specification of the minimum strength (intensity difference) of the edge to search for
nSearchLines	UDINT	Width of the search windows, i.e. the number of search lines (3, 5, 7, ...), centered around the lines specified by aInnerPoint and aOuterPoint1, aOuterPoint2
hrPrev	HRESULT	HRESULT indicating the result of previous operations (If SUCCEEDED(hrPrev) equals false, no operation is executed.)

In/Outputs

Name	Type	Description
fAngle	REAL	Returns the angle between the detected edges (radians)
aInnerPoint	TcVnPoint2_REAL	Position inside the angle to measure, from which to start the edge search process (in the direction of aOuterPoint1 and aOuterPoint2)
aOuterPoint1	TcVnPoint2_REAL	Position where the search process for edge 1 ends
aOuterPoint2	TcVnPoint2_REAL	Position where the search process for edge 2 ends

Return value

HRESULT

Further information

The F_VN_MeasureAngleBetweenEdges function localizes two linear edges and measures the angle between them.

Parameter

Input image

The ipSrcImage input image must be a 1-channel grayscale image.

Angle ^{(Return value)}

The fAngle parameter returns the angle between the localized edges.

Depending on the bAngleInDegrees parameter, the fAngle angle is specified in radians (FALSE) or in degrees (TRUE).

Position information

To localize the edges, the common starting point (aInnerPoint) and the two target points (aOuterPoint1, aOuterPoint2) must first be specified. The position of the starting point must be within the angle to be measured from which the edge search process is started. The search process ends at the respective destination points.

Parameters for edge localization

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

Expert parameters

The F_VN_MeasureAngleBetweenEdgesExp expert version contains additional parameters.

Application

The measurement of an angle between two linear edges looks like this, for example:

hr := F_VN_MeasureAngleBetweenEdges(
    ipSrcImage         := ipImageIn,
    fAngle             := fAngle,
    aInnerPoint        := aInnerPoint, 
    aOuterPoint1       := aOuterPoint1,
    aOuterPoint2       := aOuterPoint2,
    eEdgeDirection     := TCVN_ED_LIGHT_TO_DARK,
    fMinStrength       := fMinStrength, 
    nSearchLines       := nSearchLines, 
    hrPrev             := hr);

Samples

Measure Angle Between Edges

Related functions

ClosestPointsBF for calculating the closest points in two point clouds
MeasureAngleBetweenEdges for measuring the angle between two edges
MeasureEdgeDistance for measuring the average distance between two edges
MeasureMinEdgeDistance for measuring the minimum distance between two edges

Required License

TC3 Vision Metrology 2D