[Insight-developers] Calculators: Buffered or Requested regio ns?

[Miller, James V (Research)]

Stephen,

I think there are times when you want the min/max to be over the entire
image and there are times when you may want it to be computed over a
particular region.

Jim

-----Original Message-----
From: Stephen R. Aylward [mailto:aylward at unc . edu]
Sent: Thursday, June 12, 2003 12:23 PM
To: Luis Ibanez
Cc: Miller, James V (Research); Insight-developers (E-mail)
Subject: Re: [Insight-developers] Calculators: Buffered or Requested
regions?


Hi,

I am probably being slow today....shouldn't image calculators always be 
over the entire image?   I think it would be confusing if the min and 
max for an image would seem to change if the minimummaximum calculator 
is called with a subregion because of threading/streaming.

Or are we going to add logic so that min and max (for example) remain 
valid for an image when only a subregion is being processed by a 
particular thread.   Actually, can we process a thread without 
processing a whole image to init its min and max?

Okay, I really am being slow and not following this.   help!  :)

Thanks,
Stephen

Luis Ibanez wrote:
> 
> Hi Jim,
> 
> That sounds like a good idea.
> 
> It will be pretty useful to select the region over which the
> computation is going to be performed.  We could still agree
> in using the RequestedRegion() as the default region.
> 
> 
>   Luis
> 
> 
> 
> -------------------------------------
> Miller, James V (Research) wrote:
> 
>> I was just looking through some of the calculators.  The 
>> MinimumMaximumImageCalculator performs its calculation across the 
>> RequestedRegion. The OtsuThresholdImageCalculator performs its 
>> calculation over the BufferedRegion.
>>  
>> So there is an inconsistency here.  Besides the inconsistency, the 
>> Otsu method uses the MinimumMaximum to determine how to build its own 
>> histogram.  So the range of values for its histogram is based on the 
>> pixels in the RequestedRegion but it determines a threshold from the 
>> histogram based on the BufferedRegion.  This inconsistency could bias 
>> the threshold calculated.
>>  
>> At a minimum, I would think the calculators should be consistent.  I 
>> could make a case for either region being appropriate (more than I 
>> want to get into here).  Perhaps the calculators should take a region 
>> over which to perform the calculation?
>>  
>>  
>> *Jim Miller*
>> */_____________________________________/*
>> /Visualization & Computer Vision//
>> /GE Research/
>> /Bldg. KW, Room C218B/
>> /P.O. Box 8, Schenectady NY 12301/
>>
>> //_millerjv at research . ge . com <mailto:millerjv at research . ge . com>_/
>>
>> /_james . miller at research . ge . com_/
>> /(518) 387-4005, Dial Comm: 8*833-4005, /
>> /Cell: (518) 505-7065, Fax: (518) 387-6981/
>>
>>  
> 
> 
> 
> 
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-- 
===========================================================
Dr. Stephen R. Aylward
Associate Professor of Radiology
Adjunct Associate Professor of Computer Science and Surgery
http://caddlab . rad . unc . edu
aylward at unc . edu
(919) 966-9695