In most use cases of the BSpline for registration, the programmer just wants a reasonable  initialization the BSpline locations.  Determining what is "reasonable" is quite difficult because of so many parameters that needed to be set.  This function greatly simplifies the generation of the most common initialization parameters for BSplines, and if it is used, allows one place for making bug fixes that have evolved over the many years that have affected BSplines initialziation (i.e the addition of Direction to images, the fixing of the round function, the center of pixel corrections so that boundaries are properly comptuted).

The authors assume that a simpile initializer that only requires a fixedImage reference space, and the number of grid locations in each direction are all that is needed to initialize BSplines for registration in the most common use.

A review of several BSpline based registration algorithms (both inside the ITK source code, and in our own labs code) revealed that the these cases were attempting to do a simple initialization of the BSplines in the most common and straight forward way.  Unfortunately many of the actual implementations were slightly different due to many factors: 1) the example code copied to create the application, and 2) when the application was originally written.

The source code is provided.  There is enough detail to replicate their work.

This is now being place into the Review section of ITK, and is being incorporated into external to ITK for several other local lab packages.

Yes.

It is in a usable form.

Excellent code quality. 

There is not much data needed for this.

Very wide interest.  Hopefully it will become the defacto way to initialize  BSpline registration algorithms when the "straight forward" implementation is the intended gird placement.