F_VN_DetectBlobsExp

Detects blob-contours. Applies a threshold, a contour search and offers several options for filtering the found contours. Provides easy setup for multiple thresholds and combination of results. (expert function)
Can use available TwinCAT Job Tasks for executing parallel code regions.
Can return partial results when canceled by Watchdog.

Syntax

Definition:

FUNCTION F_VN_DetectBlobsExp : HRESULT
VAR_INPUT
    ipSrcImage     : ITcVnImage;
    ipBlobContours : Reference To  ITcVnContainer;
END_VAR
VAR_IN_OUT
    stParams       : TcVnParamsBlobDetection;
    aOffset        : TcVnPoint;
END_VAR
VAR_INPUT
    hrPrev         : HRESULT;
END_VAR

Inputs

Name	Type	Description
ipSrcImage	ITcVnImage	Source image (USINT or REAL, 1 channel or 3 channel (3 channel input is expected to be RGB and internally converted to Gray))
ipBlobContours	Reference To ITcVnContainer	Returns a container which is filled with the found contours (ContainerType_Vector_Vector_TcVnPoint2_DINT; The elements of this container are single contours. Non-zero interface pointers are reused.)
hrPrev	HRESULT	HRESULT indicating the result of previous operations (If SUCCEEDED(hrPrev) equals false, no operation is executed.)

In/Outputs

Name	Type	Description
stParams	TcVnParamsBlobDetection	Parameters to filter the detected contours.
aOffset	TcVnPoint	Offset by which every contour point is shifted

Return value

HRESULT

Further information

The function F_VN_DetectBlobsExp is the expert version of F_VN_DetectBlobs. It contains additional parameters.

Parameter

Input image

The input image ipSrcImage must be a 1-channel or 3-channel image of the type USINT or REAL. 3-channel images are interpreted as RGB and converted internally into grayscale images.

List of contours found ^{(Return value)}

All contours found in the input image are returned in the container ipBlobContours.

Parameters for blob detection

The parameters stParams of the structure TcVnParamsBlobDetection define which features a contour in the input image must have in order to be found and returned.

Offset ^(Expert)

The offset aOffset defines constant X/Y values by which all contour points are shifted. This can be helpful when contours are sought in an ROI and their positions should be referenced to the original image.

Related functions

F_VN_FindContours(Exp) for general contour finding
F_VN_FindContourHierarchyExp with return of the hierarchy
F_VN_DetectBlobs with integrated filtering of the contours

Required License

TC3 Vision Base

System Requirements

Development environment	Target platform	PLC libraries to include
TwinCAT V3.1. 4024.44 or later	PC or CX (x64) with PL50, e.g. Intel 4-core Atom CPU	Tc3_Vision