Homography

Find the homography (perspective transformation) between two planar point sets.

Syntax

Definition:

HRESULT Homography(
    HRESULT                  hrPrev,
    ITcVnContainer*          ipSrcPoints,
    ITcVnContainer*          ipDestPoints,
    TcVnMatrix3x3_LREAL&     aPerspectiveTransform,
    ETcVnEstimationAlgorithm eAlgorithm = EA_DEFAULT,
    double                   fReprojThreshold = 3,
    ITcVnContainer**         pipInlierMask = nullptr,
    ULONG                    nMaxIterations = 2000,
    double                   fConfidence = 0.995
)

Parameters

Name

Type

Default

Description

hrPrev

HRESULT

 

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

ipSrcPoints

ITcVnContainer*

 

Container with at least 4 source points (ContainerType_Vector_TcVnPoint2_REAL)

ipDestPoints

ITcVnContainer*

 

Container with destination points (same number as ipSrcPoints, ContainerType_Vector_TcVnPoint2_REAL)

aPerspectiveTransform

TcVnMatrix3x3_LREAL&

 

Returns the perspective transformation matrix, which transforms the source points to the destination points

eAlgorithm

ETcVnEstimationAlgorithm

EA_DEFAULT

Estimation algorithm

fReprojThreshold

double

3

Maximum allowed reprojection error to treat a point pair as an inlier (only for RANSAC, RHO)

pipInlierMask

ITcVnContainer**

nullptr

Returns a mask marking the inliers (optional, set to 0 if not required; ContainerType_Vector_SINT; only for RANSAC, LMEDS)

nMaxIterations

ULONG

2000

Maximum number of RANSAC iterations

fConfidence

double

0.995

Confidence (0..1)

Homography 1: Return value

HRESULT

Required License

TC3 Vision Base

System Requirements

Development environment

Target platform

PLC libraries to include

TwinCAT V3.1.4024.59 or later

PC or CX (x64) with min. PL50, e.g. Intel 4-core Atom CPU

Tc3_Vision