Table Of Contents

Caliper Tool (G Dataflow)

Last Modified: June 25, 2019

Finds edge pairs along a specified path in the image.

This node performs an edge extraction and finds edge pairs based on specified criteria, such as the distance between the leading and trailing edges and edge polarity.

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image in

Reference to the source image.

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pixel coordinates

Array containing the coordinates of the pixels to inspect.

You can obtain the pixel coordinates from an ROI descriptor using the ROI Profile node.

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edge parameters

Cluster defining the characteristics of the filter used to detect the edges.

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contrast

Threshold for the contrast of the edge.

Only edges with a contrast greater than this value are used in the detection process. contrast is defined as the difference between the average pixel intensity before the edge and the average pixel intensity after the edge.

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filter width

Number of pixels that the node averages to find the contrast at either side of the edge.

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steepness

Slope of the edge.

This value represents the number of pixels that correspond to the transition area of the edge.

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subpixel information

Cluster containing information about subpixel analysis.

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subpixel accuracy

Number of samples to obtain from a pixel.

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interpolation type

Method used to perform the interpolation.

Name Value Description
quadratic 1

Uses the quadratic formula to compute the pixel location

cubic spline 2

Uses cubic splines to compute the pixel location

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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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caliper parameters

Inputs for finding edge pairs.

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polarity

Polarity of the leading and trailing edge in the search process.

The following values are possible:

Name Description
none Polarity of the edges is ignored.
dark-light The leading edge has a dark-to-light polarity, and the trailing edge has a light-to-dark polarity.
light-dark The leading edge has a light-to-dark polarity, and the trailing edge has a dark-to-light polarity.
dark-dark The leading edge has a dark-to-light polarity, and the trailing edge has a dark-to-light polarity.
light-light The leading edge has a light-to-dark polarity, and the trailing edge has a light-to-dark polarity.
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separation

Desired distance between the leading and trailing edges of an edge pair.

Edge pairs with separation distance outside the range [separation - separation dev., separation + separation dev.] are ignored. If you set this parameter to 0, the node finds all edge pairs.

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separation dev.

Tolerance value for the separation between the edges.

This value influences the score of the detected edge pairs.

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image out

Reference to the source image.

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caliper report

Array of clusters that contain the following information about the detected edge pairs.

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edge1 position

Location of the leading edge.

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edge1 contrast

Contrast of the leading edge.

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edge2 position

Location of the trailing edge.

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edge2 contrast

Contrast of the trailing edge.

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separation

Computed distance in pixels between the edges in the edge pair.

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score

Unused part of report.

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edge coordinates

Array of point clusters consisting of the spatial coordinates of the detected edges.

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number of edge pairs

Number of detected edge pairs.

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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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