NAME

fitrad -- Fit a function to circular image subrasters

USAGE

fitrad images

PARAMETERS

images

List of input images to process. Any image template can be used.

outroot = ""

The output root image names. This name is preppened to each input image name in order to get the actual output image name. If null an ".out" string is appended to the input image name.

option = "fit"

The output image option. The choices are:

fit

An image is created from the function fit to the image subsraster. The fit is made equal to the input image outside the subraster.

difference

The difference between the input image and the fit (i.e. residuals). The fit is made equal to zero outside the subraster.

ratio

The ratio of the image and fit. The fit is made equal to one outside the subraster.

xcenter = INDEF, ycenter = INDEF

Center coordinates of the image subraster. If INDEF the center of the image is used.

radius = INDEF

The maximum radius of the image subraster from the center defined above. All pixels out of this radius will not be processed at all. If INDEF the maximum radius within the image is used.

ringavg = "none"

The ring averaging method. The choices are:

none

No averaging is done.

median

The azimuthal median of the pixel values is used.

mode

The azimuthal mode of the pixel values is used.

mean

The azimuthal mean of the pixel values is used.

minpts = INDEF

The minimum number of pixels in a given ring when averaging.

minwith = INDEF

The minimum ring width when averaging. The actual ring width may be increased if the number of pixels in the ring is less than this value.

function = spline3

Function to be fit to the resulting radial profile. The functions are "legendre" (legendre polynomial), "chebyshev" (chebyshev polynomial), "spline1" (linear spline), and "spline3" (cubic spline). The functions may be abbreviated.

order = 1

The order of the polynomials or the number of spline pieces.

low_reject = 0., high_reject = 0.

Rejection limits below and above the fit in units of the residual sigma.

niterate = 1

Number of rejection iterations.

grow = 0.

When a pixel is rejected, pixels within this distance of the rejected pixel are also rejected.

interactive = yes

Run the task iteractively ?.

verbose = yes

Print status information while the program is running ?. This option is usefull to know the status of processing for large images.

calctype = "real"

Internal calculation type. It can be real or double .

graphics = "stdgraph"

Graphics output device for interactive graphics.

cursor = ""

Graphics cursor input.

DESCRIPTION

For each image in the list, the task fits radial profiles to circular image subrasters, either interactively or non-interactively.
If ringavg=none the task calculates the radius for each pixel, and a fit is made to the resulting radial profile. Otherwise the task divides the image in concentric annulii, and averages all the pixel values in each annulus according to the averaging method selected.
Averaging is also controlled by the minwidth and minpts parameters. At least one of them must be defined or the task will abort with an error message. If minwidth is undefined then the annulii will have an even number of pixels defined by minpts . Otherwise, if minwidth is defined, then each annulus will have an even width with a variable number of pixels in each ring. The minimum number of pixels in all rings can be constrained to be grater than a certain value if the minpts parameter is also defined.
The output of the program is an image, of the same dimension of the corresponding input image, created from the function fit, the difference between the original image and the fit, or the ratio between the original image and the fit. The pixel type of this image will be defined by the calctype parameter, and not from the input image pixel type.

SEE ALSO

fit1d