[Insight-users] How does the ImportFilter work ?

[Dan Mueller]

Hi Agnès,

itkImportImageFilter creates an image around the buffer provided to
the filter (ie. if you have the buffer in memory, no further memory is
allocated for the pixels).

If you then use the imported image in a processing pipeline, each
processing filter will -- typically -- create a new output image (ie.
allocate a new pixel buffer). Therefore the original imported buffer
is not changed. You can see this in itkImageSource (from which all
itkImageToImageFilters derive):

  /** The GenerateData method normally allocates the buffers for all of the
   * outputs of a filter. Some filters may want to override this default
   * behavior. For example, a filter may have multiple outputs with
   * varying resolution. Or a filter may want to process data in place by
   * grafting its input to its output. */
  virtual void AllocateOutputs();

This comment alludes to the solution:
Code/Common/itkInPlaceImageFilter. Running your processing operation
"in place" means that the output will be stored in the incoming pixel
buffer. To enable this feature you can call the following on any
filter which derives from itkInPlaceImageFilter:
    filter->InPlaceOn();

Unfortunately, not all processing operations can run in place (for
example, operations which change the image resolution, or pixel type).
Hopefully the processing operation you wish to perform derives from
itkInPlaceImageFilter...

HTH

Cheers, Dan

On 30 April 2010 17:31, Agnes Masson-Sibut <agnes.massonsibut at gmail.com> wrote:
> Hello everyone,
>
> I'm getting an issue when I use an ImportFilter to create an image using an
> existed buffer.
>
> In fact, when I do some operations on an image I read from a file, no
> problem. But when I try to do the same operations on the image created from
> a buffer, it seems to me that the operations are performing on a copy of the
> buffer in the image, and not on the original buffer of the image. So that,
> when I try to save my image, the modifications due to the operations do not
> appear in the saved file.
>
> So my question is : Do I have to do something special with the import filter
> so that the object image I get can be filtered by my operations the same way
> the image I get from reading a file ?
>
> Thanks a lot.
>
> --
> Agnès Masson-Sibut
> Étudiante au doctorat
> Lissi, Université Paris Est Créteil
> Aesculap SAS, Dpt R&D Software
> tél : 06-73-60-52-91