Update

[gdcm.git] / Doc / Website / HowToUseGdcm.html

<pre>
{{{
This is a vi-able/notepad-able document to (try to) explain in a few words 
how to use efficently gdcm.
-->Feel free to send/add your comments/suggestions/modifications.
-->Don't try to 'beautify' this page.
(I plane to rewrite it in html, as soon as there is enough 'content' within it)

HTH
Jean-Pierre Roux

------------------------------------------------------------------------

0) Intro
========
1) How to Read a DICOM file
===========================
1-1) using raw C++
1-1-1) A single file
1-1-1-1) Deal with the file header
1-1-1-2) Load the 'pixels' in memory
1-1-1-3) Get the value of a single Dicom DataElement 
1-1-1-4) Get the value of a Dicom Sequence  
1-1-2) A File Set

1-2) using VTK
1-2-1) A single file
1-2-2) A File Set

1-3) using ITK
1-3-1) A single file
1-3-2) A File Set

1-4) Retrictions for Python users

2) How to write DICOM file
==========================
2-1) using raw C++
2-1-1) A single file
2-1-1-1) Deal with optional DataElements
2-1-1-1-1) Add a single Dicom DataElement // TODO
2-1-1-1-2) Add a Dicom Sequence           // TODO
2-1-2) A File Set

2-2) using VTK

2-3) using ITK

2-4) Retrictions for Python users

3) Some 'Command line' utilities
================================
3-) PrintFile
3-) exSerieHelper
3-) exXCoherentFileSet

3-) AnonymizeNoLoad
3-) AnonymizeMultiPatient
3-) AnonymizeDicomDir

3-) ReWrite
3-) RawToDicom
3-) exMoveImagesToSingleSerieUID

3-) vtkgdcmViewer2
3-) vtkgdcmSerieViewer2

3-) PrintDicomDir
3-) MakeDicomDir

----------------------------------------------------------------------------

0) Intro
========

If you are not familiar with DICOM files, use :

PrintFile filein=yourDicomFile.dcm

and have a look at the output.
You'll see a lot of self explanatory (?) lines, e.g.

D 0008|0021 [DA]   [Series Date]     [20020524]
D 0008|0060 [CS]   [Modality]        [US]
D 0018|602c [FD]   [Physical Delta X][0]
D 0020|0013 [IS]   [Instance Number] [5 ]
D 0028|0010 [US]   [Rows]            [480]
D 0011|0010 [  ]   [gdcm::Unknown]   [DLX_PATNT_01]
D 0028|1222 [OW]   [Segmented Green Palette Color Lookup Table Data]
                                 ===> [gdcm::Binary data loaded;length = 113784]

0008|0021 : 'Group Number'|'Element Number' -> The Element identifier
Have a look at gdcm/Dicts/dicomV3.dic for the whole list of Elements
 
DA        : The 'Value Representation' : DA for Date, US for Unsigned Short, ...
Have a look at gdcm/Dicts/dicomVR.dic for the set of possible values

[Series Date] : The 'official' English name of the Element
(When *you* have to deal with a given Element, its meaning should be clear for
*you*)

[20020524] : the value, printed in a human readable way.

If something like :
D 0028|1222 [OW] [Segmented Green Palette Color Lookup Table Data]
                                 ===> [gdcm::Binary data loaded;length = 113784]
is displayed, it means that it's a 'long' binary area, gdcm (I) decided not to
show.

D 0011|0010 [  ]   [gdcm::Unknown]   [DLX_PATNT_01]
is a 'Private (or Shadow) Element', depending on the manufacturer.
It's *not* known within the 'official' Dicom Dictionnary.
Except if someone told you, you cannot guess the meaning of such an element.
Probabely, you'll never have to deal with Shadow Elements (hope so!).

You can find also something like : 

S 0018|6011 [SQ]                       [Sequence of Ultrasound Regions]
   |  --- SQItem number 0
   | D fffe|e000 [UL]                               [Item]
   | D 0018|6018 [UL]             [Region Location Min X0] [32]
   | D 0018|601a [UL]             [Region Location Min Y0] [24]
   | D 0018|601c [UL]             [Region Location Max X1] [335]
   | D 0018|601e [UL]             [Region Location Max Y1] [415]
   | D 0018|602c [FD]                   [Physical Delta X] [0.0382653]
   | D 0018|602e [FD]                   [Physical Delta Y] [0.0382653]
   |  --- SQItem number 1
   | D fffe|e000 [UL]                               [Item]
   | D 0018|6018 [UL]             [Region Location Min X0] [336]
   | D 0018|601a [UL]             [Region Location Min Y0] [24]
   | D 0018|601c [UL]             [Region Location Max X1] [639]
   | D 0018|601e [UL]             [Region Location Max Y1] [415]
   | D 0018|602c [FD]                   [Physical Delta X] [0.0382653]
   | D 0018|602e [FD]                   [Physical Delta Y] [0.0382653]
   |  --- SQItem number 2
   | D fffe|e000 [UL]                               [Item]
   | D 0018|6018 [UL]             [Region Location Min X0] [32]
   | D 0018|601a [UL]             [Region Location Min Y0] [40]
   | D 0018|601c [UL]             [Region Location Max X1] [63]
   | D 0018|601e [UL]             [Region Location Max Y1] [103]
   | D 0018|6024 [US]         [Physical Units X Direction] [0]
   | D 0018|6026 [US]         [Physical Units Y Direction] [0]
   | D 0018|602c [FD]                   [Physical Delta X] [0]
   | D 0018|602e [FD]                   [Physical Delta Y] [0]

0018|6011 is a 'Sequence' (SQ), composed of various Sequence Items(SQItem)
Each SQItem is a set of Elements (an Element may be a DataElement (D) or a
Sequence (S), recursively, within any level of embedding :

S 0029|263d [SQ]                                                                   []
   |  --- SQItem number 0
   | D fffe|e000 [UL]                                                              [Item ]
   | D 0008|0000 [UL]                                                       [Group Length] [12]
   | D 0008|0001 [UL]                                               [Length to End (RET) ] [28776]
   | D 0029|0000 [UL]                                                       [Group Length] [28764]
   | D 0029|002a [LO]                                                    [Private Creator] [SPI-P-Private_ICS Release 1;6 ]
   | D 0029|2a02 [LO]                                                                   [] [PERFUSION_MR_T2STAR_GAMMA_VARIATE_ANALYSER]
   | S 0029|2a06 [SQ]                                                                   []
   |    |  --- SQItem number 0
   |    | D fffe|e000 [UL]                                                              [Item ]
   |    | D 0008|0000 [UL]                                                       [Group Length] [12]
   |    | D 0008|0001 [UL]                                               [Length to End (RET) ] [20]
   |    | D fffe|0000 [UL]                                                       [Group Length]
   |    |  --- SQItem number 1
   |    | D fffe|e000 [UL]                                                              [Item ]
   |    | D 0008|0000 [UL]                                                       [Group Length] [12]
   |    | D 0008|0001 [UL]                                               [Length to End (RET) ] [194]
   |    | D 0029|0000 [UL]                                                       [Group Length] [182]
   |    | D 0029|002a [LO]                                                    [Private Creator] [SPI-P-Private_ICS Release 1;6 ]
   |    | S 0029|2a07 [SQ]                                                                   []
   |    |    |  --- SQItem number 0
   |    |    | D fffe|e000 [UL]                                                              [Item ]
   |    |    | D 0008|0000 [UL]                                                       [Group Length] [12]
   |    |    | D 0008|0001 [UL]                                               [Length to End (RET) ] [100]
   |    |    | D 0029|0000 [UL]                                                       [Group Length] [88]
   |    |    | D 0029|002a [LO]                                                    [Private Creator] [SPI-P-Private_ICS Release 1;6 ]
   |    |    | D 0029|2a0a [US]                                                                   [] [1]
   |    |    | D 0029|2a0b [US]                                                                   [] [2]
   |    |    | D 0029|2a0c [US]                                                                   [] [2]
   |    |    | D 0029|2a0d [US]                                                                   [] [1]
   |    |    | D 0029|2a10 [US]                                                                   [] [1]
   |    |    | S 0029|2a2e [SQ]                                                                   []
   |    |    |    |  --- SQItem number 0
   |    |    |    | D fffe|e000 [UL]                                                              [Item ]
   |    |    |    | D 0008|0000 [UL]                                                       [Group Length] [12]
   |    |    |    | D 0008|0001 [UL]                                               [Length to End (RET) ] [2266]
   |    |    |    | D 0029|0000 [UL]                                                       [Group Length] [2254]
   |    |    |    | D 0029|0025 [LO]                                                    [Private Creator] [SPI-P-Private_ICS Release 1;1 ]
   |    |    |    | D 0029|0027 [LO]                                                    [Private Creator] [SPI-P-Private_ICS Release 1;3 ]
   |    |    |    | D 0029|0028 [LO]                                                    [Private Creator] [SPI-P-Private_ICS Release 1;4 ]
   |    |    |    | D 0029|2500 [SL]                                                                   [] [43]
   |    |    |    | D 0029|256b [FD]                                                                   [] [0.5]
   |    |    |    | D 0029|2700 [LO]                                                                   [] [L1]
   |    |    |    | D 0029|276a [FL]                                                                   [] [0.35]
   |    |    |    | S 0029|27c0 [SQ]                                                                   []
   |    |    |    |    |  --- SQItem number 0
   |    |    |    |    | D fffe|e000 [UL]                                                              [Item ]
   |    |    |    |    | D 0008|0000 [UL]                                                       [Group Length] [12]
   |    |    |    |    | D 0008|0001 [UL]                                               [Length to End (RET) ] [110]
   |    |    |    |    | D 0029|0000 [UL]                                                       [Group Length] [98]
   |    |    |    |    | D 0029|0027 [LO]                                                    [Private Creator] [SPI-P-Private_ICS Release 1;3 ]
   |    |    |    |    | D 0029|27b0 [SL]                                                                   [] [0]
   |    |    |    |    | D 0029|27b1 [FL]                                                                   [] [0]
   |    |    |    |    | D 0029|27b2 [FL]                                                                   [] [0]
   |    |    |    |    | D 0029|27b4 [FL]                                                                   [] [0]
   |    |    |    |    | D 0029|27b9 [FL]                                                                   [] [1]   
   | S 0029|2a14 [SQ]                                                                   []
   |    |  --- SQItem number 0
   |    | D fffe|e000 [UL]                                                              [Item ]
   |    | D 0008|0000 [UL]                                                       [Group Length] [12]
   
Probabely, you'll never have to deal with Sequences (hope so!).

1) How to Read a DICOM File
===========================

1-1) using raw C++
------------------

1-1-1) A single file
--------------------

1-1-1-1) Deal with the file header

The first step is to load the file header :

           gdcm::File *f = new gdcm::File();
                  f->SetLoadMode(LD_NOSEQ);              | depending on what
                  f->SetLoadMode(LD_NOSHADOW);           | you want *not* 
                  f->SetLoadMode(LD_NOSEQ | LD_NOSHADOW);| to load from the
                  f->SetLoadMode(LD_NOSHADOWSEQ);        | target file
           f->SetFileName(fileName);
           f->Load( );

Note :
The 'long' Data Element (>4096 char) are not loaded by default
You may modify this default length :
           f->SetMaxSizeLoadEntry(int yourOwnMaxSize);
Or ask to force the loading of given Data Elements, whatever their size is:  
            f->AddForceLoadElement (uint16_t group, uint16_t elem);
before calling gdcm::File::Load();

Note :
Except if you are really aware about it, do *not* use SetLoadMode().
LD_ALL is the default.

Check if the file is gdcm-readable.

           if ( !f->IsReadable() )
             std::cout << "major troubles on [" << f->GetFileName() <<"]"
                       << std::endl;

Decide if this is a 'File Of Interest' for you.
Check some fields, e.g

           std::string StudyDate           = f->GetEntryString(0x0008,0x0020);
           std::string PatientName         = f->GetEntryString(0x0010,0x0010);
           std::string PatientID           = f->GetEntryString(0x0010,0x0020);
           std::string PatientSex          = f->GetEntryString(0x0010,0x0040);
           std::string Modality            = f->GetEntryString(0x0008,0x0060);

(or whatever you feel like ...)

1-1-1-2) Load the 'pixels' in memory

Next step is to load the pixels in memory.
Uncompression (JPEG lossless, JPEG lossy, JPEG 2000, RLE, ...) 
is automatically performed if necessary.

           gdcm::FileHelper *fh = gdcm::FileHelper::New(f);
           void *imageData = fh->GetImageDataRaw();
           uint32_t dataSize = fh->GetImageDataRawSize();

Generally, you work on 'Grey level' images (as opposed to RGB images).
Depending on the Pixel size (8/16/32 bits) and the Pixel Type (signed/unsigned),
you cast the imageData

          std::string pixelType = f->GetPixelType();
  
Possible values are : 

- "8U"  unsigned  8 bit,
- "8S"    signed  8 bit,
- "16U" unsigned 16 bit,
- "16S"   signed 16 bit,
- "32U" unsigned 32 bit,
- "32S"   signed 32 bit,
- (NEITHER 'float' NOR 'double' pixels in DICOM!)
   
           int dimX = f->GetXSize();
           int dimY = f->GetYSize();
           int dimZ = f->GetZSize(); // meaningfull only for 'Volumes' or 'multiframe files'
           int dimT = f->GetTSize(); // meaningfull only for 4D objects (?)

Now, you can enjoy your image !

Sometimes, you deal with 'colour' images :-(
They may be stored, on disc, as :
     RGB pixels, 
     RGB planes, 
     YBR pixels, 
     YBR planes
     Grey level images + LUT.

You'll get an 'RGB Pixels' image in memory if you use: 

           gdcm::FileHelper *fh = gdcm::FileHelper::New(f);
           void *imageData = fh->GetImageData();
           uint32_t dataSize = fh->GetImageDataSize();

If you don't want to convert a "Grey level images + LUT" into "RGB Pixel image" use
           gdcm::FileHelper *fh = gdcm::FileHelper::New(f);
           void *imageData = fh->GetImageDataRaw();
           uint32_t dataSize = fh->GetImageDataRawSize();

1-1-1-3) Get the value of a single Dicom DataElement 

1-1-1-3-1) as a std::string

- some DataEntries are 'human readable' (those whose VR is AE, DA, DS, PN, SH, TM)
  Get their value using group number-element number :
  std::string patientName = f->GetEntryString(0x0010,0x0010);
  
- Some DataEntries are stored with their own binary representation, but maybe you feel like 
  to get them in a 'human readable' form (those whose VR is FL, FD, SL, SS, UL, US)
  Get their value using group number-element number : 
  std::string rowNumber =f->GetEntryString(0x0028, 0x0010);// nb of Rows
  
  (of course, the very often used DataEntries have their own accessors :
  e.g. GetXsize, GetYSize, GetSpacing, GetImageOrientationPatient, GetImagePositionPatient,
       GetRescaleSlope, GetRescaleIntercept, GetNumberOfScalarComponents, etc -see gdcmFile.h-)
  

1-1-1-3-3) as a void* pointer
- Some DataEntries are stored with their own binary representation, and you want to get them 'as they are'.
  You will have to cast them, according to the knowledge you have about them.
  LutRedData = (uint8_t*)f->GetEntryBinArea( 0x0028, 0x1201 ); 
   
1-1-1-4) Get the value(s) of a Dicom Sequence           

Actually, a 'Dicom Sequence' is composed of a list a 'Sequence Items',
each Sequence Item is a set of DataElement (that can be a Sequence Element, recursively).
You have to get the Sequence element, to get its number of Sequence items, to iterate on each one.
e.g.:

SeqEntry *seqEntry = f->GetSeqEntry(0x3006,0x0020); //Structure Set ROI sequence
unsigned int n = seqEntry->GetNumberOfSQItems();    // useless : just to see !
currentItem = seqEntry->GetFirstSQItem(); // Get the first ROI
while (currentItem != NULL) {
   std::string roiName = currentItem->GetEntryString(0x3006,0x0026);  //ROI name
   std::string roiDescr = currentItem->GetEntryString(0x3006,0x0028); //ROI description
   ...
   // do what you want with the current ROI
   currentItem = seqEntry->GetNextSQItem(); // Get the next ROI
}


1-1-2) A File Set
-----------------

If you are 150 % sure of the files you're dealing with, just read the files you
feel like, and concatenate the pixels.

Sometimes you are not sure at all (say : you were given a CDROM with an amount
of images, laying in a Directories tree-like structure, you don't know anything
about the Patients, and so on)

A class gdcm::SerieHelper is designed to help solving this problem.
Use it as follows.

    gdcm::SerieHelper *sh = gdcm::SerieHelper::New();
    while (int i=0; i < nbOfFiles; i++) {
       sh->AddFileName(currentFileName[i]);
    }
    
You can also pass a 'root directory', and ask or not for recursive parsing.
    gdcm::SerieHelper *sh = gdcm::SerieHelper::New();
    sh->SetDirectory(yourRootDirectoryName, true); // true : recursive parsing

Files are 'splitted' into as many 'Single Serie UID File Set' 
  as Series Instance UID ( 0020|000e );

// -------- skip this one, for a first reading ! -----------

Sometimes, the Serie UID is not enough to disseminate properly the images.
We may want to disseminate into multiple sub serie when needed.

Use :
void SerieHelper::SetUseSeriesDetails(bool s);
   /// This function will add the following DICOM tag as being part of a
   /// 'fake' uid. :
   /// 0020 0011 Series Number
   /// 0018 0024 Sequence Name
   /// 0018 0050 Slice Thickness
   /// 0028 0010 Rows
   /// 0028 0011 Columns 

If it's not enough for you, use :    
void SerieHelper::AddSeriesDetail(uint16_t group, uint16_t elem, bool convert);

std::string SerieHelper::CreateUniqueSeriesIdentifier(gdcm::File *inFile);
void SerieHelper::CreateDefaultUniqueSeriesIdentifier();

You may also create a "tokenizable' File Identifier of your own, using :
void SerieHelper::AddSeriesDetail(uint16_t group, uint16_t elem, bool convert);
and
std::string SerieHelper::CreateUserDefinedFileIdentifier(gdcm::File *inFile);
and use it as you feel like.

// ------------ Resume reading, here !--------------------
 
If you want to 'order' the files within each 'Single Serie UID File Set'
(to build a volume, for instance), use :
  
   gdcm::FileList *l = sh->GetFirstSingleSerieUIDFileSet();
   while (l)
   { 
      sh->OrderFileList(l);  // sort the list
      l = sh->GetNextSingleSerieUIDFileSet();
   } 
    
  The sorting will be performed on the ImagePositionPatient;
  if not found, on ImageNumber;
  if not found, on the File Name.
  
  Aware user is allowed to pass his own comparison function 
  (if he knows, for instance, the files must be sorted on 'Trigger Time')
  He will use the method
  void SerieHelper::SetUserLessThanFunction( bool(*) userFunc((File *,File *) ); 
  He may ask for a reverse sorting : 
  sh->SetSortOrderToReverse();
  or back to Direct Order 
  sh->SetSortOrderToDirect();
  
  If, for any reason of his own, user already get the file headers,
  he may add the gdcm::File (instead of the file name) to the SerieHelper.

    gdcm::SerieHelper *sh = gdcm::SerieHelper::New();
    while (int i=0; i < nbOfFiles; i++) {
       sh->AddFile(currentFile[i]);
    }                           
 * \warning : this method should be used by aware users only!
 *            User is supposed to know the files he want to deal with
 *           and consider them they belong to the same Set
 *           (even if their Serie UID is different)
 *           user will probabely OrderFileList() this list (actually, ordering
 *           user choosen gdm::File is the sole interest of this method)
 *           Moreover, using vtkGdcmReader::SetCoherentFileList() will avoid
 *           vtkGdcmReader parsing twice the same files.
 *           *no* coherence check is performed, but those specified
 *           by SerieHelper::AddRestriction()
 
   User may want to exclude some files.
   He will use
    void SerieHelper::AddRestriction(uint16_t group, uint16_t elem,
                                 std::string const &value, int op);
op belongs to :

/// \brief comparison operators
   GDCM_EQUAL ,
   GDCM_DIFFERENT,
   GDCM_GREATER,
   GDCM_GREATEROREQUAL,
   GDCM_LESS,
   GDCM_LESSOREQUAL
e.g. 
    gdcm::SerieHelper *sh = gdcm::SerieHelper::New();
    sh->AddRestriction(0x0010,0x0040,"F",GDCM_EQUAL);      // Patient's Sex
    sh->AddRestriction(0x0008,0x0060,"MR",GDCM_DIFFERENT); // Modality 
    while (int i=0; i < nbOfFiles; i++) { 
    ...
User wants to deal only with Female patient, any Modality but MR (why not?)
   
Maybe user knows there are several images with the same position
and *no dicom field* may discriminates them.
He wants to drop the 'duplicate images'
   
     sh->SetDropDuplicatePositions(true);

Sometimes the previous stuff is *not enough* !

Within a SingleSerieUIDFileSet, you can have have various orientations,
or various positions, at various times. (not only various position , at a single
time, for a single orientation).

User may consider that dealing only with the 'Series Instance UID' 
is not enough and wishes to 'refine' the image selection :

Suppose he has a Single Serie UID File Set (gdcm::FileList).
He may ask to split it into several 'X Coherent File Sets' (X stands for
'Extra').

gdcm::SerieHelper *s;
gdcm::XCoherentFileSetmap xcm;
gdcm::FileList *l = s->GetFirstSingleSerieUIDFileSet(); // or what you want


 The following methods must be called by user, depending on 
 what *he* wants to do, at application time.
  - *he* only  knows what his Series contain ! - 
 They return a std::map of Filesets (actually : a std::map of std::vector<gdcm::File* >).
 
He may ask for 'splitting' on the Orientation:
           gdcm::XCoherentFileSetmap xcm = s->SplitOnOrientation(l);
   
He may ask for 'splitting' on the Position:
           gdcm::XCoherentFileSetmap xcm = s->SplitOnPosition(l);
   
He may ask for 'splitting' on the any DataElement you feel like :   
           gdcm::XCoherentFileSetmap xcm = s->SplitOnTagValue(l, group,elem);

 
He can now work on each 'X Coherent File Set' within the std::map

for (gdcm::XCoherentFileSetmap::iterator i = xcm.begin();
                                         i != xcm.end();
                                       ++i)
{

   // ask for 'ordering' according to the 'Image Position Patient'
   // Sorting the Fileset (*) is mandatory!
   // ( computing an accurate Series ZSpacing -whenever possible- is a side effect ...)
     
   s->OrderFileList((*i).second);  // sort the XCoherent Fileset
}  

(have a look at gdcm/Examples/exXCoherentFileSet.cxx for an example)

1-2) using VTK
--------------
a vtkGdcmReader() method ( derived from vtkReader() ) is available.

1-2-1) A single file
--------------------

   vtkGdcmReader *reader = vtkGdcmReader::New();
   reader->SetFileName( yourDicomFilename );      
   reader->SetLoadMode( yourLoadMode); // See C++ part 
   reader->Update();
   vtkImageData* ima = reader->GetOutput();
   int* Size = ima->GetDimensions();   
 // -> Enjoy it.     

1-2-2) A File Set
-----------------

If you are 150 % sure of the files you're dealing with, just 'add' the files you
feel like:

   vtkGdcmReader *reader = vtkGdcmReader::New();
   for(int i=1; i< yourNumberOfFiles; i++)
         reader->AddFileName( yourTableOfFileNames[i] );     
   reader->SetLoadMode( yourLoadMode); // See C++ part 
   reader->Update();
   vtkImageData* ima = reader->GetOutput();
   int* Size = ima->GetDimensions();
 // -> Enjoy it.
 
 Warning : The first file is assumed to be the reference file.
 All the inconsistent files (different sizes, pixel types, etc) are discarted
 and replaced by a black image ! 
 
      User is allowed to pass a Pointer to a function of his own
      to allow modification of pixel order (i.e. : Mirror, UpsideDown, )
      to gdcm::FileHeleper, using SetUserFunction(userSuppliedFunction)

      described as : void userSuppliedFunction(uint8_t *im, gdcm::File *f);

      NB : the "uint8_t *" type of first param is just for prototyping.
        User will Cast it according what he found with f->GetPixelType()
        See vtkgdcmSerieViewer for an example
 

Many users expect from vtkGdcmReader it 'orders' the images 
(Actually, that's the job of gdcm::SerieHelper ...)
When user knows the files with same Serie UID have same sizes, 
same 'pixel' type, same color convention, ... 
the right way to proceed is as follow :

        gdcm::SerieHelper *sh= new gdcm::SerieHelper();
   //      if user wants *not* to load some parts of the file headers
        sh->SetLoadMode(yourLoadMode);

   //      if user wants *not* to load some files
        sh->AddRestriction(group, element, value, operator);
        sh->AddRestriction( ...
        sh->SetDirectory(directoryWithImages);

   //      if user *knows* how to order his files
        sh->SetUserLessThanFunction(userSuppliedComparisonFunction);
   //      or/and
   //      if user wants to sort reverse order
        sh->SetSortOrderToReverse();
   
   //      here, we suppose only the first 'Single SerieUID' Fileset is of interest
   //      Just iterate using sh->NextSingleSerieUIDFileSet()
   //      if you want to get all of them
        gdcm::FileList *l = sh->GetFirstSingleSerieUIDFileSet();

   //      if user is doesn't trust too much the files with same Serie UID
        if ( !sh->IsCoherent(l) )
           return; // not same sizes, or not same 'pixel type' -> stop
   
   // Maybe user knows there are several images with the same position
   // and *no dicom field* may discriminates them.
   // He wants to drop the 'duplicate images'
   
        sh->SetDropDuplicatePositions(true); 

   // Sorting the Fileset (*) is mandatory!
   // ( computing an accurate Series ZSpacing is a side effect ...)  
        sh->OrderFileList(l);

        vtkGdcmReader *reader = vtkGdcmReader::New();
   //      if user wants to modify pixel order (Mirror, TopDown, ...)
   //      he has to supply the function that does the job
   //      (a *very* simple example is given in vtkgdcmSerieViewer.cxx)
        reader->SetUserFunction (userSuppliedFunction);

   //      to pass a 'Single SerieUID' Fileset as produced by gdcm::SerieHelper
        reader->SetCoherentFileList(l);
        reader->Update();


//-----------------
(*)
User may also pass an 'X Coherent Fileset', created by one of the following
methods : (see 1-1-2 for more details)
 
           xcm = sh->SplitOnOrientation(l); 
           xcm = sh->SplitOnPosition(l);   
           xcm = sh->SplitOnTagValue(l, groupelem[0],groupelem[1]);
//----------------


You can see a full example in vtk/vtkgdcmSerieViewer2.cxx
e.g.
vtkgdcmSerieViewer dirname=Dentist mirror
vtkgdcmSerieViewer dirname=Dentist reverse
vtkgdcmSerieViewer dirname=Dentist reverse upsidedown


1-4) Retrictions for Python users
---------------------------------

None of the methods receiving a function pointer, or a gdcm::File as a parameter
is wrapable by swig.
:-(


2) How to write DICOM file
==========================

2-1) using raw C++
------------------

2-1-1) A single file
--------------------
In C++, if you have already the pixels in main memory, 
you just have to process as follow :

--> Create an empty gdcm::File
        gdcm::File *file = gdcm::File::New();

        std::ostringstream str;

// --> Set the mandatory fields
  // Set the image size
        str.str("");
        str << sizeY;
        file->InsertEntryString(str.str(),0x0028,0x0010,"US"); // Rows
        str.str("");
        str << sizeX;
        file->InsertEntryString(str.str(),0x0028,0x0011,"US"); // Columns
        str.str("");
        str << sizeZ;
        file->InsertEntryString(str.str(),0x0028,0x0008, "IS"); // Nbr of Frames
  // Set the pixel type
        str.str("");
        str << componentSize; //8, 16, 32
        file->InsertEntryString(str.str(),0x0028,0x0100,"US"); // Bits Allocated
        str.str("");
        str << componentUse; // may be 12 or 16 if componentSize =16
        file->InsertEntryString(str.str(),0x0028,0x0101,"US"); // Bits Stored
        str.str("");
        str << componentSize - 1 ;
        file->InsertEntryString(str.str(),0x0028,0x0102,"US"); // High Bit
  // Set the pixel representation // 0/1
        str.str("");
        str << img.sign;
        file->InsertEntryString(str.str(),0x0028,0x0103, "US"); // Pixel Representation
  // Set the samples per pixel // 1:Grey level, 3:RGB
        str.str("");
        str << components;
        file->InsertEntryString(str.str(),0x0028,0x0002, "US"); // Samples per Pixel

//--> Set Optional fields
      se further how to deal with optional fields

//--> Create a gdcm::FileHelper
       gdcm::FileHelper *fileH = gdcm::FileHelper::New(file);

//--> Tell the FileHelper what you did for creating the image:

      // gdcm cannot guess how user built his image 
      //  (and therefore cannot be clever about some Dicom fields)
      // It's up to the user to tell gdcm what he did.
      // -1) user created ex nihilo his own image and wants to write it 
      //     as a Dicom image.
      // USER_OWN_IMAGE
      // -2) user modified the pixels of an existing image.
      // FILTERED_IMAGE
      // -3) user created a new image, using existing a set of images 
      //    (eg MIP, MPR, cartography image)
      //  CREATED_IMAGE
      // -4) user modified/added some tags *without processing* the pixels 
      //     (anonymization, ...)
      //  UNMODIFIED_PIXELS_IMAGE
      // -Probabely some more to be added
      //(see gdcmFileHelper.h for more explanations)

      // Use :
      
      fileH->SetContentType(GDCM_NAME_SPACE::USER_OWN_IMAGE);
      fileH->SetContentType(GDCM_NAME_SPACE::FILTERED_IMAGE);
      fileH->SetContentType(GDCM_NAME_SPACE::CREATED_IMAGE);
      fileH->SetContentType(GDCM_NAME_SPACE::UNMODIFIED_PIXELS_IMAGE);
      
      // depending on what you did before!

//--> Set the compression type : 
      fileH->SetWriteTypeToJPEG();      // lossles compression        
      fileH->SetWriteTypeToJPEG2000();  // lossles compression 
      fileH->SetWriteTypeToDcmExplVR(); // Explicit Value Representation (no compression)
      fileH->SetWriteTypeToDcmImplVR(); // Implicit Value Representation (no compression)
      
      fileH->SetWriteModeToRaw();       // Probabely you don't want to convert any LUT into RGB pixels ...

//--> Set the Image Data
       fileH->SetImageData((unsigned char *)imageData,size);
      // ( Casting as 'unsigned char *' is just to avoid warnings.
      // It doesn't change the values. )
      // or
       fileH->SetUserData((unsigned char *)imageData,size); // performs compression, when required
            
//-> Write !      
      fileH->Write(fileName.str());

//This works for a single image (singleframe or multiframe)

2-1-1-1) Deal with optional DataElements          // TODO : finish it
    Any Data Element may be added (it's up to the user to understand what he is doing!)
    The supplied methods 'InsertXxx' will create the DataElement or replace it if it already exists.  
    Have a look at gdcm/Dict/dicomV3.dic to see what are the various DICOM fields, with their VR.
    
2-1-1-1-1) Add a single Dicom DataElement          // TODO : finish it

   use :
   DataEntry * File::InsertEntryString(std::string const &value,
                                   uint16_t group, uint16_t elem,
                                   VRKey const &vr = GDCM_VRUNKNOWN);
  
   // (e.g. : patient name, patient ID, ... , or what you want,
   //  using their Dicom identifier, and 'VR'
      file->InsertEntryString("MyOwnPatient" ,0x0010,0x0010,"PN"); // 0010 0010 : Patient's Name
   
    DataEntry * File:InsertEntryBinArea(uint8_t *binArea, int lgth,
                                    uint16_t group, uint16_t elem,
                                    VRKey const &vr = GDCM_VRUNKNOWN);  
   
2-1-1-1-2) Add a Dicom Sequence           // TODO : finish it
   SeqEntry * File::InsertSeqEntry(uint16_t group, uint16_t elem);
   
2-1-2) A File Set
-----------------
/// \todo : write it!


// If you deal with a Serie of images, it up to you to tell gdcm, for each image,
// what are the values of
// 0020 0032 DS 3 Image Position (Patient)
// 0020 0037 DS 6 Image Orientation (Patient)

// You will probabely want that all the images of your file set belong to the same 'Serie'


2-2) using VTK
--------------

/// \todo : write it!

2-2-1) A single file
--------------------

/// \todo : finish it!

// User of the CVS version of VTK 5 may set some 'Medical Image Properties'
// Only the predefined DataElements are available :
// PatientName, PatientID, PatientAge, PatientSex, PatientBirthDate, StudyID
// It's reasonably enough for any 'decent use'
//
// todo : explain how to use it.
//vtkMedicalImageProperties

   // Aware user is allowed to pass his own gdcm::File *, 
   //  so he may set *any Dicom field* he wants.
   // (including his own Shadow Elements, or any gdcm::SeqEntry)
   // gdcm::FileHelper::CheckMandatoryElements() will check inconsistencies,
   // as far as it knows how.
   // Sorry, not yet available under Python.
   //vtkSetMacro(GdcmFile, gdcm::File *);
   
void vtkGdcmWriter::SetGdcmFile(gdcm::File *);

   // gdcm cannot guess how user built his image 
   //  (and therefore cannot be clever about some Dicom fields)
   // It's up to the user to tell gdcm what he did.
   // -1) user created ex nihilo his own image and wants to write it 
   //     as a Dicom image.
   // USER_OWN_IMAGE
   // -2) user modified the pixels of an existing image.
   // FILTERED_IMAGE
   // -3) user created a new image, using existing a set of images 
   //    (eg MIP, MPR, cartography image)
   //  CREATED_IMAGE
   // -4) user modified/added some tags *without processing* the pixels 
   //     (anonymization..
   //  UNMODIFIED_PIXELS_IMAGE
   // -Probabely some more to be added
   //(see gdcmFileHelper.h for more explanations)
   
   // User is allowed to use the following methods:
   
void vtkGdcmWriter::SetContentTypeToUserOwnImage()                           
void vtkGdcmWriter::SetContentTypeToFilteredImage()                            
void vtkGdcmWriter::SetContentTypeToUserCreatedImage()                        
vtkGdcmWriter::void SetContentTypeToUnmodifiedPixelsImage()
   
  // depending on what he did before!
  
                      

2-2-2) A File Set
-----------------
/// \todo : write it!


2-3) using ITK
--------------
/// \todo : write it!

2-4) Retrictions for Python users
---------------------------------
/// \todo : write it!

3) Some 'Command line' utilities  /// \todo: finish it!
================================

3-) PrintFile
3-) exSerieHelper
3-) exXCoherentFileSet

3-) AnonymizeNoLoad
3-) AnonymizeMultiPatient
3-) AnonymizeDicomDir

3-) ReWrite
3-) RawToDicom
3-) exMoveImagesToSingleSerieUID

3-) vtkgdcmViewer2
3-) vtkgdcmSerieViewer2

3-) PrintDicomDir
3-) MakeDicomDir
}}}
</pre>