1 MAKE_CUBE Output a filled cube from an uncomplete sampled cube
MAKE_CUBE
This is an image construction task which is able to produce a
filled image from one containing many blanked pixels. The reconstructed
filled image is not constrained to fit exactly the observed data points.
On the opposite, the construction is made by the analogy to a flexible
plate attached to fixed points by springs: the plate is the analogous
of the surface represented by the image, and the fixed points are the
analogous of the observed data points. By adjusting the parameter P
P = (plate stiffness) / (springs stiffness)
it is possible to control the fidelity to the original data and the
amount of smoothing involved in the image reconstruction. Low values of
P mean high fidelity to observed data, and negligible amount of
smoothing.
The original grid is first expanded by a factor EXPANSION$, new pix-
els being attributed the blanking value. Then, the minimization
proceeds iteratively to adjust the final image, until convergence is
reached. Initially blanked pixels are ignored in the convergence
criterium.
The algorithm works on cubes, processing each plane independently. It
can be used as an alternative to FILL_CUBE for oversampled images, but
works also for undersampled data.
2 P$
TASK\REAL "Smoothing parameter" P$
This is the value of the smoothing parameters. It should remain be-
tween 0.001 and 10. The higher values give stronger smoothing, and
should be used for noisy data.
2 NITER$
TASK\INTEGER "Number of smoothing iterations" NITER$
This is the number of smoothing iterations. Ten iterations are usu-
ally enough to reach convergence, unless the expansion factor is
large.
2 EXPANSION$
TASK\INTEGER "Expansion factor" EXPANSION$
This is the expansion factor for the output cube, i.e. the number of
output pixels for each input pixel along each direction. Minimum
value is 2, maximum is 10. Note that the computing time is proportional
to the number of output pixels, thus to EXPANSION$**2.
2 IN$
TASK\FILE "Input file name" IN$
This is the name of the input file.
2 OUT$
TASK\FILE "Output file name" OUT$
This is the name of the output smoothed image.
2 GUESS$
TASK\REAL "Initial value for blanked pixels" GUESS$
This is an initial guess for the original value attributed to
blanked pixels. Try to find something reasonable, usually the average
of valid pixels. Convergence can be delayed if you choose a crazy
value, since the minimization tends to produce a smooth image, but the
result doesnot depend on GUESS$.
1 ENDOFHELP