Options window of Imagetool



This window consists in two subregions (the last one is empty), the one at the top contains nonlinear options and linear options and the following has degradation options. At the very bottom there is a Help line that shows the purpose of the control the mouse is on.
Nonlinear options

Depending on the method we have the following nonlinear options:

Primal/Primal-dual
Beta stop:
Beta stop is the regularizing parameter appearing in the modified TV functional.
Beta start:
Selects the initial beta in the continuation procedure.
Beta step:
Selects the factor by which beta is decreased after a successful subproblem solution in the continuation procedure.
NWT tol:
Tolerance for the (outer) iteration.
NWT its:
Maximum number of outer iterations.
Fixed point
Beta:
Beta is the regularizing parameter appearing in the modified TV functional.
FP tol:
Tolerance for the (outer) iteration.
FP its:
Maximum number of outer iterations.
Time marching
Beta:
Beta is the regularizing parameter appearing in the modified TV functional.
Time step:
Initial time step length to ensure stability and sufficient decrease.
TM tol:
Tolerance for the (outer) iteration.
TM its:
Maximum number of outer iterations.

Linear options

The following linear options are available for the Newton-type and fixed point methods:

CG rel.tol:
relative tolerance on residual for CG stopping criterion.
CG its:
maximum number of iterations for CG.
Preconditioner:
selects the preconditioner for CG. Depending on whether there is blur or not we have the following options:

No blur:

No:
no preconditioner.
ILU:
incomplete Cholesky preconditioner (default).
DS:
diagonal scaling preconditoner.
Blur:
No:
no preconditioner.
CT+DS:
Fast cosine transform preconditioner, combined with diagonally scaling(default).
CT:
Fast cosine transform preconditioner.

Degradation options

The popup menu at the left of the degradation options region selects the type of blur. The currently supported blurs are:

None
Gaussian:
G(i,j)=e (i 2+ j 2)/(4*Theta) /K, for i=-Width, ..., Width, j=-Height, ..., Height and with K=sum(G(i,j)). Selecting this will trigger the appearance of three more windows to select the parameters above
Width
Height
Theta
Custom:
user supplied PSF, which is loaded by clicking on the Load button that appears after selecting this type of blur.

The next popup is used to choose between the two restoration strategies:

Tikhonov:
need to supply the alpha parameter in the corresponding control.
Constraints:
need to supply an estimate of the variance of the noise in the corresponding control.

The SNR control allows to specify some amount of noise so that it matches the entered number. It is tightly related to the Variance control.

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