[Insight-developers] Image/ImageAdaptor/DataAccessor modification

[Luis Ibanez]

Hi,

Relations between ImageAdaptor, Image and DataAccessor
have slightly changed.

Before a DataAccessor was only a type with static methods
defined in Image and ImageAdaptor.  Iterators used it to 
convert types during pixel access.

Now a member variable of DataAccessor type is declared
in Image and ImageAdaptor. In this way, the Accessor can have
some state information.

This is used to make possible a N-th element adaptor.

   itkNthElementImageAdaptor
   itkNthElementDataAccessor

Given and image whose pixels are of type container:
itkVector, itkPoint, std::vector... and in general, any type
that provides a operator[](unsigned int)  method.

The image can be adapted to make it look like a scalar
image whose pixels are the n-th elements of the adapted
image.

The selection of the element number can be done at run time 
using the SelectNthElement() method in NthElementImageAdaptor.

                          +--------------+ 
                          |              |   Here it looks 
                          +----+  N-th   |   like a scalar 
+---------------------------+  | element |   image. Each pixel   
| Image<vector<float,4>, 3> |->| Image   |   is the n-th element
+---------------------------+  | Adaptor |   of the corresponding
                          +----+         |   pixel in the adapted
                          | m_ElementNum |
                          +--------------+

---


Pixel access is supposed to be inlined. 
That seems to be the case in VC++ and gcc, 
...but if you notice any big change in performance
on pixel access, I'll double check the iterator's 
Get/Set method.


Thanks,


Luis