[vtkusers] Problem in loading big images using vtkimagereader

[Michael Jackson]

Windows does have 64 bit file functions available. You just have to special
case for them. When I get to work I will post the code that I use in my own
projects.

-----
Mike Jackson                      www.bluequartz.net
Principal Software Engineer       mike.jackson at bluequartz.net
BlueQuartz Software               Dayton, Ohio

On Aug 12, 2010, at 5:21, "Leo van Ruijven" <LvRuijven at gmx.com> wrote:

As Mike said, you do not have to change the API to correct the issue. Just
use 64 bit precision calculations inside the methods (for vtkImageReader2
the method SeekFile() must also be corrected).


However, on my computer (Windows XP and Visual Studio 8) that did not yet
solve the problem. In windows the file positioning functions are still not
fully 64 bit. So in vtkImageReader::SeekFile() the line:


   this->File->seekg(streamStart, ios::beg);


did not work if streamStart is too large. But the following workaround does
work on my system:


  this->File->seekg(0, ios::beg);
  while (streamStart > 0x2000000) {
      this->File->Seek(0x2000000, ios::cur);
      streamStart -= 0x2000000;
  }
  if (streamStart > 0) this->File->seekg(streamStart, ios::cur);



I don't know how to change the vtk source code. otherwise I would have
corrected the bug myself. But If somebody is interested in my version of
vtkImageReader2, just let me know.


Leo.




there _is_ but the actual code in the vtkImageReader2 class uses the
"long" and not the "vtkIdType" which would help solve the problem. An
example is the following that was posted to the ParaView mailing list:

In the void vtkImageData::AllocateScalars(); method the following
should be used:

  vtkIdType extent[6] ={ this->Extent[0], this->Extent[1], this-
 >Extent[2],
                         this->Extent[3], this->Extent[4], this-
 >Extent[5]};

instead of
  const int* extent = this->Extent;

In the case of vtkImageReader2 it is probably "long" instead of int.
Either way on Windows, both are a 32 bit integer no matter how you
compile it.

___________________________________________________________
Mike Jackson                      www.bluequartz.net
Principal Software Engineer       mike.jackson at bluequartz.net
BlueQuartz Software               Dayton, Ohio



On Aug 11, 2010, at 9:35 AM, John Drescher wrote:

>> http://public.kitware.com/pipermail/paraview/2008-March/007422.html
>>
>> Is when I came across the issue. I did not keep track of what the
>> eventual
>> "fixes" were but somewhere (probably a private email) I think it
>> was said
>> that a fix was difficult because the API for a lot of filters would
>> need to
>> be changed.
>>   In the most draconian fix the use of "long" should just be
>> banned, but
>> this would cause all sorts of backwards compatibility issues.
>>
>
> Isn't there an option when building VTK to use 64 bit ids? I have
> never used that so I am not sure how much of the code supports this.
>
> John



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