CFwhm Class Description


The CFwhm class is used to compute the Full Width at Half Maximum for an image feature. This class provides methods for calculating the FWHM and for working with control parameters. The centroid computation collects points around a central position, then fits a Gaussian + Constant model to the data. The fit parameters lead to the FWHM value, the background value, and the peak value of the point spread function. Both peaks and valleys can be measured. The Calc method usually uses a centroid position as the center point of the FWHM calculation.

Usage

Construction

Object = new_fwhm()

Object = CFwhm:new()

Destruction

Object:delete()

Properties

The properties in the table below may be accessed directly. However, it is better programming style to access them using the provided Get... and Set... methods when available.

radiusX

The pixel radius for computing the centroid position in the x direction.

radiusY

The pixel radius for computing the centroid position in the y direction.

trackX

The pixel radius for tracking the peak or valley in the x direction from the initial position to the centroid position.

trackY

The pixel radius for tracking the peak or valley in the y direction from the initial position to the centroid position.

bPositive

True if centroids are computed for peaks, or false if computed for valleys.

nMinIter

The minimum number of iterations used in fitting the radial intensity profile.

bSnWeighting

True to weight the data by signal to noise ratio when computing the fit.

bAutoCentroid

True computes the centroid before fitting the radial profile data.

nInitialFwhm

The trial value, in pixels, of the FWHM used in the iterative solution.

nMaxRadius

The maximum radius in pixels, of the radial profile sample.

Creation - Non-class Functions

This function is normally used to create a new CFwhm object as an alternative to the class-based new method.

new_fwhm

Creates a new instance of a CFwhm object.

Construction and Destruction - Class Methods

new

Creates a new instance of a CFwhm object.

delete

Deletes the instance of the CFwhm object.

Data Member Access

GetSign

Returns true if the FWHM and centroid are being computed for peaks, rather than for valleys.

GetSample

Returns the centroid sample radius in x and y directions.

GetTracking

Returns the centroid tracking radius in x and y directions.

SetSign

Sets the centroid calculation to use peaks (true) or valleys (false).

SetSample

Sets the centroid sample radius in x and y directions to the specified number of pixels.

SetTracking

Sets the centroid tracking radius in x and y directions to the specified number of pixels.

GetAutoCentroid

Returns true if the auto-centroid flag is set and the FWHM uses a centroid position.

SetAutoCentroid

Sets the auto-centroid flag true or false.

GetMaxRadius

Returns the maximum profile sampling radius, in pixels.

SetMaxRadius

Sets the maximum profile sample radius.

Operations

Calc

Calculates the Fwhm and, optionally, the centroid position for near starting coordinate x,y.

Fwhm

Returns the computed FWHM value.

Peak

Returns the computed peak value.

Bg

Returns the computed background value.

X

Returns the computed x coordinate of the centroid position.

Y

Returns the computed y coordinate of the centroid position.

Related Topics

Script Classes

 

 


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