Table Of Contents

Edge Detection Filter (G Dataflow)

Last Modified: October 26, 2017

Extracts the contours in gray-level values.

Any image connected to the input image dst must be the same image type connected to image src. The image type connected to the input image mask must be an 8-bit image. The connected source image must have been created with a border capable of supporting the size of the processing matrix. For example, a 3 × 3 matrix has a minimum border size of 1. The border size of the destination image is not important. This node modifies the source image. If you need the original source image, create a copy of the image using the Copy Image node before using this node.

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Canny filter parameters

Cluster containing the following filter parameters:

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Sigma

Sigma of the Gaussian smoothing filter that the node applies to the image before performing the edge detection.

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HThresh

High threshold input that defines the upper percentage of pixel values in the image from which the edge detection algorithm chooses the seed or starting point of an edge segment. Values range from 0 to 1.

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LThres

Low threshold input that is multiplied by the HThresh value to define a lower threshold for all the pixels in an edge segment.

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WindowSize

WindowSize defines the size of the Gaussian filter that the VI applies to the image. The size must be an odd number.

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image src

Reference to the source image.

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image mask

8-bit image that specifies the region of the small image to be copied.

Only pixels in the image src image that correspond to a non-zero pixel in the mask image are copied. All other pixels keep their original values. The entire image is processed if image mask is not connected.

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image dst

Reference to the destination image.

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method

Type of edge-detection filter to use.

The following filters are valid:

Name Description
Differentiation Processing with a 2 × 2 matrix
Gradient Processing with a 2 × 2 matrix
Prewitt Processing with a 3 × 3 matrix
Roberts Processing with a 2 × 2 matrix
Sigma Processing with a 3 × 3 matrix
Sobel Processing with a 3 × 3 matrix

Default: Differentiation

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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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threshold value

Minimum pixel value that appears in the resulting image.

NI recommends not using a value greater than 0 for this type of processing because the results from this processing are usually dark and not dynamic.

Default: 0

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image dst out

Reference to the destination image.

If image dst is connected, image dst out is the same as image dst. Otherwise, image dst out refers to the image referenced by image.

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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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