Table Of Contents

Find Circular Edge (G Dataflow)

Last Modified: June 25, 2019

Locates a circular edge in a search area.

This node locates the intersection points between a set of search lines and the edge of an object.

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options

Cluster defining the parameters of the edge detection algorithm and the information that is overlaid on the resulting image.

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search direction

Direction in which edge detection is performed.

Name Value Description
outside to inside 0 1

Searches the ROI from the outer radius to the inner radius.

inside to outside 1

Searches the ROI from the inner radius to the outer radius.

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show result

Boolean that determines if the edge found is overlaid on the resulting image.

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show search area

Boolean that specifies if the search area is overlaid on the image.

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show search lines

Boolean that specifies if the search lines used to locate the edges are overlaid on the image.

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show edges found

Boolean that specifies if the locations of the edges found are overlaid on the resulting image.

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edge options

Parameters used to compute edge gradient information and detect edges.

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edge polarity

Polarity of the edges to be found.

Name Value Description
all edges 0

(Default) Searches for all edges

rising edges 1

Searches for rising edges

falling edges 2

Searches for falling edges

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kernel size

Size of the edge detection kernel.

Default: 3

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width

Number of pixels averaged perpendicular to the search direction to compute the edge profile strength at each point along the search ROI.

Default: 3

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minimum edge strength

Minimum edge strength, or gradient magnitude, required for a detected edge.

Default: 10

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interpolation type

Interpolation method used to locate the edge position.

Name Description
zero order Rounds to the nearest integral edge location
bilinear Uses bilinear interpolation to compute the edge location
quadratic Uses the quadratic formula to computer the edge location.
cubic Uses cubic splines to computer the edge location.
bilinear fixed (Default) Uses the fixed-point computation of bilinear interpolation to determine the edge location
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data processing method

Method used to process the data extracted for edge detection.

Name Description
average Averages the data extracted for edge detection
median Takes the median of the data extracted for edge detection

Default: Average

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search area color

Color to use to overlay the search area.

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search lines color

Color to use to overlay the search lines.

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edge locations color

Color to use to overlay the edge locations.

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result color

Color to use to overlay the result.

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overlay group name

Name to give the overlay group.

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image in

Reference to the source image.

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ROI descriptor

Region of Interest (ROI) within which the edge detection is performed.

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global rectangle

Coordinates of the bounding rectangle for the circular edge in the image.

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contours

Individual shapes that define an ROI.

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ID

Input that determines if the contour is the external or internal edge of an ROI.

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type

Shape type of the contour.

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coordinates

Relative position of the contour.

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circle fit options

Options used to fit the circle.

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process

Type of search performed.

Name Description
get first edge Returns the first edge.
get first + last edge Returns the first and last edge.
get all edges (Default) Returns all edges found along the search path(s).
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step size

Angle, in degrees, between each radial line in the annular region.

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max pixel radius

Length of the radius within which a point is assumed to be part of the fitted circle.

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coordinate system

Input that specifies the coordinate system to use.

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reference system

Cluster containing origin, angle (deg), and axis reference.

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origin

Point cluster that specifies the origin of the base-reference coordinate system.

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x

X-coordinate of the center of the circle.

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y

Y-coordinate of the center of the circle.

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angle (deg)

Angle that the base-reference coordinate system makes with the image coordinate system.

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axis reference

Element defined as direct or indirect.

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measurement system

Cluster containing origin, angle (deg), and axis reference.

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origin

Point cluster that specifies the origin of the base-reference coordinate system.

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x

X-coordinate of the center of the circle.

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y

Y-coordinate of the center of the circle.

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angle (deg)

Angle that the base-reference coordinate system makes with the image coordinate system.

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axis reference

Element defined as direct or indirect.

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error in

Error conditions that occur before this node runs.

The node responds to this input according to standard error behavior.

Standard Error Behavior

Many nodes provide an error in input and an error out output so that the node can respond to and communicate errors that occur while code is running. The value of error in specifies whether an error occurred before the node runs. Most nodes respond to values of error in in a standard, predictable way.

error in does not contain an error error in contains an error
If no error occurred before the node runs, the node begins execution normally.

If no error occurs while the node runs, it returns no error. If an error does occur while the node runs, it returns that error information as error out.

If an error occurred before the node runs, the node does not execute. Instead, it returns the error in value as error out.

Default: No error

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image out

Reference to the input image.

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fitted circle

Cluster that contains the position and characteristics of the fitted circle.

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center (pixels)

Coordinates of the center of the circle in pixels.

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x

X-coordinate of the center of the circle.

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y

Y-coordinate of the center of the circle.

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radius (pixels)

Radius, in pixels, of the circle formed by the detected edge.

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center (real-world)

Coordinates of the center of the circle in calibrated units.

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x

X-coordinate of the center of the circle.

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y

Y-coordinate of the center of the circle.

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radius (real-world)

Radius, in calibrated units, of the circle formed by the detected edge.

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roundness (real-world)

Roundness of the circular edge.

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average strength

Average strength, or gradient magnitude, of the detected edge.

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average SNR (dB)

Average signal-to-noise (SNR) ratio along the detected edge.

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circle found?

Boolean that indicates if a circular edge is found.

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coordinate system dup

Reference to the coordinate system.

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reference system

Cluster containing origin, angle (deg), and axis reference.

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origin

Point cluster that specifies the origin of the base-reference coordinate system.

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x

X-coordinate of the center of the circle.

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y

Y-coordinate of the center of the circle.

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angle (deg)

Angle that the base-reference coordinate system makes with the image coordinate system.

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axis reference

Reference to the axis defined as direct or indirect.

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measurement system

Cluster containing origin, angle (deg), and axis reference.

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origin

Point cluster that specifies the origin of the base-reference coordinate system.

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x

X-coordinate of the center of the circle.

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y

Y-coordinate of the center of the circle.

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angle (deg)

Angle that the base-reference coordinate system makes with the image coordinate system.

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axis reference

Reference to the axis defined as direct or indirect.

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error out

Error information.

The node produces this output according to standard error behavior.

Standard Error Behavior

Many nodes provide an error in input and an error out output so that the node can respond to and communicate errors that occur while code is running. The value of error in specifies whether an error occurred before the node runs. Most nodes respond to values of error in in a standard, predictable way.

error in does not contain an error error in contains an error
If no error occurred before the node runs, the node begins execution normally.

If no error occurs while the node runs, it returns no error. If an error does occur while the node runs, it returns that error information as error out.

If an error occurred before the node runs, the node does not execute. Instead, it returns the error in value as error out.

Where This Node Can Run:

Desktop OS: Windows

FPGA: Not supported

Web Server: Not supported in VIs that run in a web application


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