[Insight-users] Reading portion of the image without loading the whole image into the memory

[Matt McCormick]

Hi Yan,

Streaming will only occur if the filter is streamable and it has been
implemented as a streamable filter.  Unfortunately the NrrdImageIO is
not implemented as a streaming reader at this time, so it will always
load the entire image to memory.  For more information, see the
CanStreamRead method on itk::ImageIOBase.

HTH,
Matt

On Tue, Aug 14, 2012 at 9:22 PM, yan xu <xy198908 at gmail.com> wrote:
>  Hi, David,
>         I'm afraid it doesn't work, the codes are following for 16bit nrrd.
> The memory still increases up to the size of the image not the region of
> image I defined. Is it due to the image type or something? The codes are
> following:
>
> UShortImageType::IndexType index;
> index[0] = startX;
> index[1] = startY;
> index[2] = startZ;
>
> UShortImageType::SizeType size;
> size[0] = sizeX;
> size[1] = sizeY;
> size[2] = sizeZ;
>
> UShortImageType::RegionType region;
> region.SetIndex( index);
> region.SetSize( size);
>
> ushortImageReader::Pointer reader = ushortImageReader::New();
> reader->SetFileName(fileName);
> reader->GetOutput()->SetRequestedRegion(region);
>
> try
> {
> reader->Update();
> }
> catch ( itk::ExceptionObject &err)
> {
> std::cout << "Error in bin_image_writer: " << err << std::endl;
> }
>
>
> Yan
>
>
> On Tue, Aug 14, 2012 at 4:08 PM, David Doria <daviddoria at gmail.com> wrote:
>>
>> On Tue, Aug 14, 2012 at 4:59 PM, yan xu <xy198908 at gmail.com> wrote:
>>>
>>> Hi, all
>>>       I'm facing a problem to read only portion of the image to test the
>>> algorithm since the whole image is too big for the memory. I have tried
>>> using the itk pipeline through extractimage filter, but I don't think it
>>> works. The memory still goes larger and larger. My image type is 16bit nrrd.
>>> What I hope is that the only the desired region of the image is loaded into
>>> the memory. Is there a solution for that? Thank you!
>>
>>
>> I've never done it, but you could try this:
>>
>> http://www.itk.org/Wiki/ITK/Examples/SimpleOperations/RequestedRegion
>>
>> on your ImageReader.
>>
>> David
>
>
>
>
> --
> Yan Xu
> Research Assistant
> Bio-Image Analytics Laboratory
> Department of Electrical and Computer Engineering
> University of Houston
>
>
>
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