[Insight-developers] How to support vector of complex as a pixel type in ImageIOBase?

[Kent Williams]

This is all about being able to read and write images with a vector type 
of itk::Vector<std::complex<float>,N>.

NIfTI supports A) vectors of components per pixel and B) Complex types 
as components.  Currently, the itk::NiftiImageIO doesn't support the 
complex component types, but could be extended to support them.

Except for this: itk::ImageIOBase doesn't understand a vector of 
complex. You can create an image with a pixel type of 
itk::Vector<std::complex<float>,3> but when 
itk::ImageIOBase::SetPixelTypeInfo is called, it fails.

The problem stems from the supported types of pixel types in ImageIOBase:

    /** Enums used to manipulate the pixel type. The pixel type provides
       * context for automatic data conversions (for instance, RGB to
       * SCALAR, VECTOR to SCALAR). */
      typedef  enum {UNKNOWNPIXELTYPE,SCALAR,RGB,RGBA,OFFSET,VECTOR,
                     POINT,COVARIANTVECTOR,SYMMETRICSECONDRANKTENSOR,
                     DIFFUSIONTENSOR3D,COMPLEX,FIXEDARRAY}  IOPixelType;

      /** Enums used to manipulate the component type. The component type
       * refers to the actual storage class associated with either a
       * SCALAR pixel type or elements of a compound pixel.
       */
      typedef  enum {UNKNOWNCOMPONENTTYPE,UCHAR,CHAR,USHORT,SHORT,UINT,INT,
                     ULONG,LONG, FLOAT,DOUBLE} IOComponentType;

You can have a Vector of any type mentioned in the IOComponentType, but 
there's no COMPLEX in IOComponentType.

There are two things I could do to address this: 1) Add a VECTORCOMPLEX 
type to IOPixelType -- in which case the IOComponentType will refer to 
the scalar type of the Complex number's real and imaginary type. Or 2) 
Add COMPLEX types to IOComponentType.

The first seems less than general, the second is stylistically confusing 
because COMPLEX could be the IOPixelType  or the IOComponentType.

NIfTI files supports Complex pixel component types (complex<float>, 
complex<double> and complex<long double>), and it supports vectors of 
any of the component types. It can even support an NxM Matrix of 
Complex.  But for itk::NiftiImageIO to take advantage of that support, 
itk::ImageIOBase needs to address the Complex pixel component type.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://www.itk.org/mailman/private/insight-developers/attachments/20060707/f0a0fb35/attachment.htm