[Dcmlib] Re: [Fwd: Re: Images Axial Acquisition order]

[Mathieu Malaterre]

> I think we initialy made a lot of stupid things, in vtkGdcmReader.
> - BuildFileListFromPattern is probabely 100% unused, because almost no 
> dicom file name in the world can be built from a pattern

Yes and no. It's like saying why do we ever look at ImageNumber they are 
hardly ever used... I have seen cases where the filename respect a 
patern. Furthermore we can also resort the filename that respect the 
pattern, the pattern never meant: "This is the order we will read the 
files"...
Anyway I agree this does not seem very usefull.

> - AddFileName leads to an unusable unsorted set of files

Ok I have 500 files. I know I am interested in 100 of them let say: 
150-250. How do I tell vtkGdcmReader I am only interested in those 
(remember we still don't have selection by volume(*)).

> - When the files are read, vtkGdcmReaderforgets immediately they were 
> Dicom files (whe delete gdcm::File)

evil...

> - when the volume is read, it's too late to transform its planes.

yes and no. ITK has a low level notion of orientation directly in the 
itk::Image definition. It's just that VTK does not. BUT to display a 
vtk::Image, we use Actor that have a notion of Orientation. So yes the 
orientation is really application level, and gdcm shall never ever try 
to reorganize pixel to apply a transformation ! This is not our goal, 
this is not our main focus.
So please no code to shuffle pixel around in gdcm.

> I think we have to allow user (you) to pass vtkGdcmReader a function 
> that describes the transformations he wants to apply on each image 
> immediately after reading.


More than a transformation I would rather see a 'Style'. As you describe 
in a previous mail there is a more Dentist one, a more conventional for 
XYZ...
So I would rather see the transformation being as a subclass of 
gdcm::Transformation. Something like:

gdcm::Transformation t;
t->SetModeToDentist();
or
t->SetMode( gdcm::Dentist );

vtkGdcmReader->SetTransformation( t->GetOutput() )

Mathieu
(*) In VTK to read 100 slices from a serie we would do:

reader =  bla
reader->SetFilePattern()
reader->SetExtent(0,511, 0, 511, 100, 250);
                                  ^^^^^^^^
And then the reader understand the user is only interested in a 
subvolume of the serie and therefore will only read the necessarie 
files. It's just a matter of notation (plus we don't have implemented 
the Extent notion).