[Insight-developers] HOWTO: For testing -- force streaming write?

[Williams, Norman K]

I'm a bit confused about actually testing streaming writing in an ImageIO
test.


in
ITK/Modules/IO/Base/test/itkImageFileWriterStreamingPastingCompressingTest1
.cxx, it looks as though the only thing done to force streaming is to call
ImageIOBase::SetNumberOfStreamDivisions.

Which is what I copied.

But in stepping through itk::HDF5ImageIO, I noticed that instead of
breaking up the write operation into several streamed sub-writes, it was
always requesting a write of the whole image at one go.

But stepping into itk::ImageFileWriter, there's this business (around line
339):

      InputImageRegionType bufferedRegion = input->GetBufferedRegion();
      if ( bufferedRegion == largestRegion )
        {
        // if so, then just write the entire image
        itkDebugMacro("Requested stream region  matches largest region
input filter may not support streaming well.");
        itkDebugMacro("Writer is not streaming now!");
        numDivisions = 1;
        streamRegion = largestRegion;
        ImageIORegionAdaptor< TInputImage::ImageDimension >::
        Convert( streamRegion, streamIORegion, largestRegion.GetIndex() );
        }


Since the input is an Image, it's buffered region is equal to it's largest
region, so it doesn't actually perform streamed writing at all.

In fact, it looks like you can't make itk::ImageFileWriter stream an input
image at all, unless you somehow monkey around with its buffered region,
something I don't even begin to understand.

Or am I missing something?



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