[vtkusers] Fast element access of vtkImageData?

[Joseph D. Wieber Jr.]

Hello,

Is there a fast way to access (get and set) elements in a vtkImageData 
object?  For instance I have two image data object with dimensions 
512x512x1 that I'm using as part of a cost table (it's convenient) for 
an algorithm.  One of them gets the output of a convolution filter and I 
do lookups into it.  The other one has to be initialized to all 1.0 
values at the beginning of the algorithm.  Then based on information 
from the first one, I set values in the second one.  The algorithm is a 
specialized Laplacian zero crossing.  I've been using the following 
template to initialize all the values to 1.0:

//-----------------------------------------------------------------------------
//TODO: This is horribly slow.  Find a smarter way!

template< typename T >
void
fillImageData(  ImageDataPtr pImageData, const T& val )
{
     int dims[ 3 ];
     pImageData->GetDimensions ( dims );
     int& xMax = dims[ 0 ];
     int& yMax = dims[ 1 ];
     int& zMax = dims[ 2 ];
     int numComponents = pImageData->GetNumberOfScalarComponents ();

     for( int z = 0; z < zMax; ++z )
     {
         for ( int y = 0; y < yMax; ++y )
         {
             for( int x = 0; x < xMax; ++x )
             {
                 for( int c = 0; c < numComponents; ++c )
                 {
                     pImageData->SetScalarComponentFromFloat ( x, y, z, 
c, val );
                 }
             }
         }
     }
}

To get and set values during the zero crossing computation I've been 
using combinations of GetScalarComponentAsFloat, and 
SetScalarComponentFromFloat and this part is also very slow.

Can someone please point me to an example that accomplishes similar 
tasks in a more efficient manner, or offer a suggestion on where to 
look?  Thank you.

Regards,

Joseph