[Insight-developers] handling of filter regions

[Miller, James V (CRD)]

Filters are responsible for producing their "output" requested region.  In the filter update process,
a filter can decide that it may need to produce more than that requested region but it has to produce
at least the output requested region.

Most filters will produce a new image that is only the size of the "output" requested region (i.e. #2
in your message).

Jim


-----Original Message-----
From: Damion Shelton [mailto:dmsst59+@pitt.edu]
Sent: Saturday, May 19, 2001 11:13 AM
To: 'insight-Developers'
Subject: [Insight-developers] handling of filter regions


Although I haven't played around much with regions (other than using them to
set the size of an image), I have a few questions on how RequestedRegion
fits into the filtering/processing scheme.

I presume the intent of a code fragment such as:

image->SetRequestedRegion(aregion);
filter->SetInput(image);
filter->Update()

would be to run the filter only on the requested region of the image. Now,
my question is how the output of the filter should be interpreted. Is it:

1) The original image, with the filtered region modified but the
non-filtered area unchanged (by "original" I mean that the output pointer is
the input pointer)
2) A new image, the same size as the filtered region.
3) A new image, the same size as the input image, with the filtered region
modified but the non-filtered area unchanged: i.e., passing through the
unfiltered portion

Obviously some filtering algorithms *must* generate new images
(shrinking/subsampling for example).

So, is there a standard approach to determining how regions behave, or is
this left up to the filter's designer? And, if I wanted versions of a filter
that do both (2) and (3), would I need to implement them separately, or just
write one and have a "behavior" flag.

Thanks,

-Damion-


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