[Insight-users] Batch resampling: error writing files of diff erent size

[Miller, James V (Research)]

Call UpdateLargestPossibleRegion() instead of Update() on the Writer.

The first time a pipeline is executed, Update() and
UpdateLargestPossibleRegion()
do the same thing.  After the first update, however, Update() always tries
to
produce the same requests as the previous call to Update().  If you change
the
file attached to the pipeline, the image size can change (as you found out),

and using the "cached" region requests is inappropriate.  Calling
UpdateLargestPossibleRegion() will force the pipeline to adapt to the image 
sizes.

In general, you want to call Update() when a pipeline or data has been
modified
but you "know" the image sizes have not changed.  After a change to the
pipeline
or data that causes a change in image sizes, you need to call
UpdateLargestPossibleRegion() or explictly manage the RequestedRegion() on
the last 
node in the pipeline.


> -----Original Message-----
> From: Jolinda Smith [mailto:jolinda@darkwing.uoregon.edu]
> Sent: Wednesday, April 30, 2003 3:19 PM
> To: insight users
> Subject: [Insight-users] Batch resampling: error writing files of
> different size
> 
> 
> Hello,
> 
> I'd like to resample several files in a batch process. I've written a
> program that parses a text file containing input filenames, output
> filenames, and resampling parameters. I set up the pipeline, call
> "SetFileName" on the reader and writer, set resampling parameters, and
> update the writer. Then I read in new filenames and parameters, set
> them, and update the writer again. However, if the size of the output
> image is larger that it was for the previous set of files, the writer
> fails (referencing memory at 0x00000 when writing metaimage output, an
> ITK exception: "error writing image data" when writing 
> analyze output).
> A stripped-down version of the code is below.
> 
> Is the buffer for the output image data not getting resized correctly?
> Is there something else I can do to make this work?
> 
> ReaderType::Pointer reader = ReaderType::New();
> WriterType::Pointer writer = WriterType::New();
> FilterType::Pointer filter = FilterType::New();
> 
> filter->SetInput( reader->GetOutput() );
> writer->SetInput( filter->GetOutput() );
> 
> while (file.good()) {
> 
>   getline(file, input_filename);
>   getline(file, output_filename);
> 
>   OutputImageType::SizeType size;
>   file >> size[0];
>   file >> size[1];
>   file >> size[2];
> 
>   reader->SetFileName(input_filename );
>   writer->SetFileName(output_filename);
>   filter->SetSize(size);
> 
>   try
>   {
>     writer->Update();
>   }
>   catch (itk::ExceptionObject& err)
>   {
>     cout << err << endl;
>     return -1;
>   }
> 
> }
> 
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