IMAQ Extract Curves VI

LabView NI Vision

IMAQ Extract Curves VI

Owning Palette: AnalysisInstalled With: NI Vision Development Module

Finds curves in an image.

IMAQ Extract Curves

ROI Descriptor specifies the region of the image in which to extract curves. This region must be a single rectangle or rotated rectangle contour. By default, the VI returns the curves for the entire image.

Global Rectangle contains the coordinates of the bounding rectangle.

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

	ID refers to whether the contour is the external or internal edge of an ROI.
	Type is the shape type of the contour.
	Coordinates indicates the relative position of the contour.

Image is a reference to the source image.

Curve Parameters is a cluster containing information about how curves are extracted from the image.

Extraction Mode specifies how the VI identifies curves in the image. Choose from the following options:

Normal (0)	(Default) Select Normal if you want the VI to make no assumptions about the uniformity of objects in the image or the image background.
Uniform Regions (1)	Select Uniform Regions if you want the VI to assume that either the objects in the image or the image background consist of uniform pixel values. This allows the VI to more accurately calculate the external curves of the objects.

Edge Threshold specifies the minimum contrast a seed point must have for it to be begin a curve. Valid values range from 1 to 360. The default value is 75.

Edge Filter Size specifies the width of the edge filter that the VI uses to identify curves in the image. The following options are available:

Fine (0)	Sets the Edge Filter Size to fine.
Normal (1)	(Default) Sets the Edge Filter Size to normal.

Min Length specifies the length, in pixels, of the smallest curve that you want the VI to identify. The VI ignores any curves that have a length less than this value. The default value is 25.

Row Search Step Size specifies the distance, in the y direction, between the image rows that the algorithm inspects for curve seed points. Valid values range from 1 to 255. The default value is 15.

Col Search Step Size specifies the distance, in the x direction, between the image columns that the algorithm inspects for curve seed points. Valid values range from 1 to 255. The default value is 15.

Max Endpoint Gap specifies the maximum gap, in pixels, between the endpoints of a curve that the VI identifies as a closed curve. If the gap is larger than this value, the VI identifies the curve as an open curve. The default value is 10.

Closed specifies whether to identify only closed curves in the image. The default value is FALSE, which specifies that the VI should identify both open and closed curves.

Subpixel is ignored by the VI.

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.

	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.
	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.
	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.

Image (dup) is a reference to the source image.

Curves is an array describing the curves found in the image.

	Points specifies the location of every point detected on the curve.
	Closed? is TRUE (Closed) when the distance between the endpoints of the curve are less than or equal to Max Endpoint Gap or FALSE (Open) when the distance between the endpoints of the curve are greater than Max Endpoint Gap.
	Curve Length returns the length of the curve.
	Min Edge Strength returns the lowest edge strength detected on the curve.
	Max Edge Strength returns the highest edge strength detected on the curve.
	Average Edge Strength returns the average of all edge strengths detected on the curve.

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.

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