[Insight-developers] filter questions

[Miller, James V (CRD)]

To clarify:

A filter's GenerateData() method is responsible for allocating the output pixel data.  The output
object is allocated by the pipeline mechanism but the pixel data is not allocated until
GenerateData() (i.e. GenerateData makes a call to outputPtr->Allocate()).

If you are writing a single threaded filter, then your filter provides the GenerateData() method and
is responsible for calling Allocate().

If you are writing a multithreaded filter, then your filter provides the ThreadedGenerateData()
method and the superclass object calls Allocate() automatically.

Jim

-----Original Message-----
From: Luis Ibanez [mailto:ibanez at cs.unc.edu]
Sent: Thursday, November 09, 2000 1:34 AM
To: lng at statsci.com; insight-developers at public.kitware.com
Subject: Re: [Insight-developers] filter questions


Hi,

Lydia Ng wrote:
>.....
> 3) FilterImageBinary used to allocate memory for the output data
>  in GenerateData(), it doesn't anymore. Why the change?
>

I made that change  in response to the new needs of the execution
model.

The allocation was done when we expected that the filter will
receive an entire input image, and using its size, will be able
to determine the size of the output image.  So the filter allocated
this output memory before being executed.

Now with the streaming model.  The filters should not allocate the
memory for the output image because the output is now imposed
as a constrain.   The filter is now told to : "produce data for filling
this particular region of the image", the filter should then determine
how much input it needs for producing this output region.

So when the filter is executed, allocations should have already 
been solved by... "someone else",  and my guess is that this 
"someone else" is the superprocess controlling the setting of 
image regions and activating the filters on each particular
piece.

Please correct me if this is a wrong assumption...

Thanks 

Luis


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