Possible fix needed in indexing docs

[humatic]

pynrrd/docs/source/background/index-ordering.rst

Line 6 in 96bf87b

NRRD stores the image elements in `row-major ordering <https://en.wikipedia.org/wiki/Row-_and_column-major_order>`_ where the row can be seen as the fastest-varying axis. The header fields of NRRD that describes the axes are always specified in the order from fastest-varying to slowest-varying, i.e., `sizes` will be equal to `(# rows, # columns)`. This is also applicable to images of higher dimensions.

I feel like this wording is either ambiguous or incorrect:

...order from fastest-varying to slowest-varying, i.e., sizes will be equal to (# rows, # columns).

Shouldn't the last bit be one of these?

• (# of cols, # of rows)
• (size of row, size of col)

For reference: https://teem.sourceforge.net/nrrd/format.html#general.4

Taking their example of a 640x480 color image, the header would be sizes: 3 640 480, which is equivalent to (# of colors, # of columns, # of rows).