IMAQ Estimate Flat Field Model VI

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Updated2023-02-21
6 minute(s) read

Owning Palette: Processing
Requires: NI Vision Development Module

Returns a flat field image by fitting a mathematical model on the supplied image.

Refer to the NI Vision Concepts Help for more information about flat field correction.

Examples

IMAQ Estimate Flat Field Model

ROI Descriptor defines the region of interest (ROI) within which the flat field operation is computed.

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 Src is a reference to the source image.

Image Dst is the reference to destination flat field image

Mask Image is the reference to the mask image. The mask image represents the background region on Image Src.

Surface Fit Options is a cluster of options used to determine the surface fit to construct the flat field image.

Model specifies the surface fitting model to use.

Polynomial (0)

Uses a 2D polynomial mathematical model to determine the image.

Sampling Grid Size is a cluster specifying the size of the grid the VI uses when fitting the Model. The larger the grid size is, the more accurate the fit will be. The time to estimate the flat field image will increase the larger the grid size is.

	SizeX is the size of the window in the x-dimension.
	SizeY is the size of the window in the y-dimension.

Polynomial Degree specifies the polynomial degree the algorithm uses to estimate the background of the image. The time to estimate the flat field image will increase the larger the degree is.

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.

Background Estimation Options is a cluster of options used to estimate the background region of Image Src.

Estimate Background? enables background estimation algorithm when set to TRUE.

Method selects the method the algorithm uses to estimate the background of the model image.

Polynomial (0)	Uses a polynomial algorithm with a specified Polynomial Degree to estimate the background.
Background Correction (1)	Performs background correction to eliminate non-uniform lighting effects and then performs thresholding using the interclass variance thresholding algorithm.
NiBlack (2)	Computes thresholds for each pixel based on its local statistics using the NiBlack local thresholding algorithm.

Polynomial Degree specifies the polynomial degree the algorithm uses to estimate the background of the image. The time to estimate the flat field image will increase the larger the degree is.

Window Size (32x32) is a cluster specifying the size of the window the VI uses when calculating a local threshold.

	SizeX is the size of the window in the x-dimension.
	SizeY is the size of the window in the y-dimension.

Niblack Deviation Factor (0.2) specifies the k constant used in the Niblack local thresholding algorithm, which determines the weight applied to the variance calculation. Valid k constants range from 0 to 1. The lower the Deviation Factor, the closer the pixel value must be to the mean value to be selected as part of a particle. Setting the Niblack Deviation Factor to 0 will increase the performance of the VI because the VI will not calculate the variance for any of the pixels.

Flat Field Image Out is the estimated flat field image.

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.

Examples

Refer to the following for an example that uses this VI.

LabVIEW\examples\Vision\Image Processing\Flat Field Estimation.vi

NI Vision for LabVIEW

Table of Contents

IMAQ Estimate Flat Field Model VI

Examples