[Insight-developers] itkLargeImageWriteReadTest and large file

[Bradley Lowekamp]

Hello,

	The itkLargeImageWriteReadTests were added to test to see if  
itk::Image can deal with image greater then 2GB or 4GB. However, they  
fail on Mac OSX despite it being 64-bits with a 8-byte long. The apple  
OS is limited to only being able to read or write a maximum of 2GB at  
a time (regardless of 32 or 64-bit build). I don't know if this is the  
only OS with this limitation. The MetaIO library writes the files in  
one large block and therefore runs into this limitation. However the  
NRRD file format appears to read and write in smaller blocks, so by  
modifying the test to  use NRRD it passes on my system. An alternative  
is to use streamed reading and writing (actually I am not sure if that  
would work to get around this for writing, as I think the  
ImageFileWriter writes the whole image if it is available even if it  
was requested to stream).

The VisibleHumamStreamReadWriteTest is a very interesting test with  
regards to large images. Currently this is running only on my mini's,  
some are 64-bit, others are 32-bit. I did not realize it at the time,  
but this means that were are processing a 16GB image on a 32-bit  
machine. I am not saying that there are not issues related to this out  
of core processing, just that it is very cool we are already doing  
this :)

Currently I am running an experimental on "victoria", which should  
show up on the dashboard shortly.

Brad

========================================================
Bradley Lowekamp
Lockheed Martin Contractor for
Office of High Performance Computing and Communications
National Library of Medicine
blowekamp at mail.nih.gov


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