F_VN_FindReferenceKeyPointsInImageExp

Searches a reference image, represented by its keypoints and corresponding descriptors, in a given source image. (expert function)
Can use available TwinCAT Job Tasks for executing parallel code regions.

Syntax

Definition:

FUNCTION F_VN_FindReferenceKeyPointsInImageExp : HRESULT
VAR_INPUT
    ipSrcKeyPoints        : ITcVnContainer;
    ipSrcDescriptors      : ITcVnImage;
    ipRefKeyPoints        : ITcVnContainer;
    ipRefDescriptors      : ITcVnImage;
    nRefImageWidth        : UDINT;
    nRefImageHeight       : UDINT;
    ipEdgePoints          : Reference To  ITcVnContainer;
    fMaxDist              : REAL;
    fMaxKnnRatio          : REAL;
    eNormType             : ETcVnNormalizationType;
    eAlgorithm            : ETcVnEstimationAlgorithm;
    fReprojThreshold      : LREAL;
    nMaxIterations        : UDINT;
    fConfidence           : LREAL;
    ipGoodMatches         : Reference To  ITcVnContainer;
    ipInlierMask          : Reference To  ITcVnContainer;
    hrPrev                : HRESULT;
END_VAR
VAR_OUTPUT
    aPerspectiveTransform : TcVnMatrix3x3_LREAL;
    nNumberOfGoodMatches  : UDINT;
    nNumberOfInliers      : UDINT;
END_VAR

Inputs

Name	Type	Description
ipSrcKeyPoints	ITcVnContainer	KeyPoints of the source image, e.g. (ContainerType_Vector_TcVnKeyPoint)
ipSrcDescriptors	ITcVnImage	Descriptors of the source image KeyPoints
ipRefKeyPoints	ITcVnContainer	KeyPoints of the reference image (ContainerType_Vector_TcVnKeyPoint)
ipRefDescriptors	ITcVnImage	Descriptors of the reference image KeyPoints
nRefImageWidth	UDINT	Width of the reference image in pixels
nRefImageHeight	UDINT	Height of the reference image in pixels
ipEdgePoints	Reference To ITcVnContainer	Returns a container with the 4 edge points of the reference image transformed into the coordinates of the source image (ContainerType_Vector_TcVnPoint2_REAL)
fMaxDist	REAL	Maximum allowed descriptor distance (-1 disables this filter criterion)
fMaxKnnRatio	REAL	Maximum allowed distance ratio between first and second best match ([0..1], -1 disables this filter criterion)
eNormType	ETcVnNormalizationType	Normalization type used for descriptor matching (HAMMING recommended for AKAZE, ORB, and BRISK. HAMMING2 is recommended for ORB if the ORB nBriefPoints parameter is 3 or 4. )
eAlgorithm	ETcVnEstimationAlgorithm	Estimation algorithm used for computing the perspective transformation between the two point sets
fReprojThreshold	LREAL	Maximum allowed reprojection error to treat a point pair as an inlier (only used if eAlgorithm is RANSAC, RHO)
nMaxIterations	UDINT	Maximum number of RANSAC iterations
fConfidence	LREAL	Confidence (0..1)
ipGoodMatches	Reference To ITcVnContainer	Returns a container with good matches (optional, set to 0 if not required; ContainerType_Vector_TcVnDMatch)
ipInlierMask	Reference To ITcVnContainer	Returns a mask marking the inliers (optional, set to 0 if not required; ContainerType_Vector_SINT; only for RANSAC, LMEDS)
hrPrev	HRESULT	HRESULT indicating the result of previous operations (If SUCCEEDED(hrPrev) equals false, no operation is executed.)

Outputs

Name	Type	Description
aPerspectiveTransform	TcVnMatrix3x3_LREAL	Returns the perspective transformation matrix, which transforms the reference points to the source points
nNumberOfGoodMatches	UDINT	Return the number of good matches
nNumberOfInliers	UDINT	Return the number of inlier matches

Return value

HRESULT

Required License

TC3 Vision Matching

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