NI Vision for LabVIEW

IMAQ Find Circular Edge 3 VI

  • Updated2023-02-21
  • 11 minute(s) read
Owning Palette: Locate Edges
Requires: NI Vision Development Module

Locates a circular edge in a search area. This VI locates the intersection points between a set of search lines and the edge of an object.

Supported Image Types

8-bit unsigned grayscale 16-bit unsigned grayscale 32-bit RGB 16-bit signed grayscale 64-bit RGB floating point grayscale 32-bit HSL

IMAQ Find Circular Edge 3

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Options is a cluster defining the parameters of the edge detection algorithm and the information that is overlaid on the result image.

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Search Direction specifies the direction in which edge detection is performed.

Outside to Inside (0)

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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Edge Options specifies the parameters used to compute edge gradient information and detect edges.

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Edge Polarity specifies the polarity of the edges to be found.

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 specifies the size of the edge detection kernel. The default is 3.

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Width specifies the number of pixels averaged perpendicular to the search direction to compute the edge profile strength at each point along the search ROI. The default is 3.

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Minimum Edge Strength specifies the minimum edge strength (gradient magnitude) required for a detected edge. The default is 10.

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Interpolation Type specifies the interpolation method used to locate the edge position.

Choose from the following options:

Zero Order (0)

Rounds to the nearest integral edge location

Bilinear (1)

Uses bilinear interpolation to compute the edge location

Bilinear Fixed (4)

(Default) Uses the fixed-point computation of bilinear interpolation to determine the edge location

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Data Processing Method is the method used to process the data extracted for edge detection.

Average (0)

(Default) Averages the data extracted for edge detection

Median (1)

Takes the median of the data extracted for edge detection

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Show Search Area determines whether the search area is overlaid on the image.

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Show Search Lines determines whether the search lines used to locate the edges are overlaid on the image.

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Show Edges Found determines whether the locations of the edges found are overlaid on the result image.

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Show Result determines whether the edge found is overlaid on the result image.

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Search Area Color specifies the color to use to overlay the search area.

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Search Lines Color specifies the color to use to overlay the search lines.

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Edge Locations Color specifies the color to use to overlay the edge locations.

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Result Color specifies the color to use to overlay the result.

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Overlay Group Name specifies name to give the overlay group.

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Image is a reference to the image in which you want to locate the circular edge.

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

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Global Rectangle contains the coordinates of the bounding rectangle for the circular edge in the image.

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Contours are each of the individual shapes that define an ROI.

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ID refers to whether the contour is the external or internal edge of an ROI.

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Type is the shape type of the contour.

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Coordinates indicates the relative position of the contour.

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Coordinate System specifies the coordinate system to use.

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Reference System is a cluster containing the following elements.

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Origin is a point cluster that specifies the origin of the base-reference coordinate system.

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X is the x-coordinate of the center of the circle.

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Y is the y-coordinate of the center of the circle.

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Angle (deg) is the angle the base-reference coordinate system makes with the image coordinate system.

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Axis Reference is defined as Direct or Indirect. Refer to Axis Type for more information.

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Measurement System is a cluster containing the following elements.

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Origin is a point cluster that specifies the origin of the base-reference coordinate system.

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X is the x-coordinate of the center of the circle.

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Y is the y-coordinate of the center of the circle.

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Angle (deg) is the angle the base-reference coordinate system makes with the image coordinate system.

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Axis Reference is defined as Direct or Indirect. Refer to Axis Type for more information.

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error in (no error) describes the error status before this VI or function runs. The default is no error. If an error occurred before this VI or function runs, the VI or function passes the error in value to error out. This VI or function runs normally only if no error occurred before this VI or function runs. If an error occurs while this VI or function runs, it runs normally and sets its own error status in error out. Use the Simple Error Handler or General Error Handler VIs to display the description of the error code. Use error in and error out to check errors and to specify execution order by wiring error out from one node to error in of the next node.

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status is TRUE (X) if an error occurred before this VI or function ran or FALSE (checkmark) to indicate a warning or that no error occurred before this VI or function ran. The default is FALSE.

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code is the error or warning code. If status is TRUE, code is a nonzero error code. If status is FALSE, code is 0 or a warning code.

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source describes the origin of the error or warning and is, in most cases, the name of the VI or function that produced the error or warning. The default is an empty string.

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Circle Fit Options specifies the options that are used to fit the circle.

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Process determines the type of search. Choose from the following values:

Get First Edge (0)

Returns the first edge.

Get First + Last Edge (1)

Returns the first and last edge.

Get All Edges (2)

(Default) Returns all edges found along the search path(s).

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Step Size is the angle, in degrees, between each radial line in the annular region.

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Max Pixel Radius specifies the length of the radius within which a point is assumed to be part of the fitted circle.

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Circle Found is a Boolean that indicates whether a circular edge is found.

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Image Out is a reference to the input image.

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Fitted Circle is a cluster that contains the position and characteristics of the fitted circle.

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Center (Pixels) lists the coordinates of the center of the circle in pixels.

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X is the x-coordinate of the center of the circle.

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Y is the y-coordinate of the center of the circle.

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Radius (Pixels) indicates the radius, in pixels, of the circle formed by the detected edge.

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Center (Real-World) lists the coordinates of the center of the circle in calibrated units.

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X is the x-coordinate of the center of the circle.

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Y is the y-coordinate of the center of the circle.

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Radius (Real-World) indicates the radius, in calibrated units, of the circle formed by the detected edge.

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Roundness (Real-World) returns the roundness of the circular edge.

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Average Strength is the average strength (gradient magnitude) of the detected edge.

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

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Coordinate System (duplicate) is a reference to the coordinate system.

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Reference System is a cluster containing the following elements.

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Origin is a point cluster that specifies the origin of the base-reference coordinate system.

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X is the x-coordinate of the center of the circle.

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Y is the y-coordinate of the center of the circle.

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Angle (deg) is the angle the base-reference coordinate system makes with the image coordinate system.

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Axis Reference is defined as Direct or Indirect. Refer to Axis Type for more information.

icclst.gif

Measurement System is a cluster containing the following elements.

inclst.gif

Origin is a point cluster that specifies the origin of the base-reference coordinate system.

isgl.gif

X is the x-coordinate of the center of the circle.

isgl.gif

Y is the y-coordinate of the center of the circle.

isgl.gif

Angle (deg) is the angle the base-reference coordinate system makes with the image coordinate system.

iu32.gif

Axis Reference is defined as Direct or Indirect. Refer to Axis Type for more information.

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error out contains error information. If error in indicates that an error occurred before this VI or function ran, error out contains the same error information. Otherwise, it describes the error status that this VI or function produces. Right-click the error out indicator on the front panel and select Explain Error from the shortcut menu for more information about the error.

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status is TRUE (X) if an error occurred or FALSE (checkmark) to indicate a warning or that no error occurred.

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code is the error or warning code. If status is TRUE, code is a nonzero error code. If status is FALSE, code is 0 or a warning code.

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source describes the origin of the error or warning and is, in most cases, the name of the VI or function that produced the error or warning. The default is an empty string.

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