As described previously in section 3.2, multiresolution images are stored in a series of separate image, image-max, and image-min variables, called resolution groups. Full-resolution data is stored under the path /minc-2.0/image/0/image, half resolution data is stored under the path /minc-2.0/image/1/image, and so on.
Only the full resolution image may be modified directly by applications. The library recalculates the reduced-resolution data for all resolution groups defined in the MINC 2.0 file, either explicitly in response to a request from the programmer, or implicitly in response to a file close operation.
In the initial implementation of MINC 2.0, thumbnail image voxels will be calculated using a simple averaging of the voxels of the next-higher resolution image. However, the MINC 2.0 library will provide an extension mechanism for programmers to implement and use more sophisticated thumbnail calculation if desired.
The use of multiple resolutions is entirely optional. The MINC library only recalculates lower-resolution images for which the resolution group entries have been defined. Not all intervening resolution groups need to be present for the file to be valid. In addition to the mandatory full-resolution data, a MINC 2.0 file could define a single 1/8 resolution thumbnail at the path /minc-2.0/image/3/image, and the library must recalculate and store only that resolution.
All thumbnail images must have the same datatype and dimension order as the full-resolution image.
The complete attribute must be used and honored for all resolutions that are defined. This attribute is used to determine the validity each of the images.