[Neuroimaging] Nibabel API change - always read as float

Satrajit Ghosh satra at mit.edu
Wed Jul 8 04:29:36 CEST 2015

hi matthew,

> We have to address ourselves to the standard as it is actually used.
> As the standard is used, there is almost never a reason to assume that
> an image with slope = 1, intercept = 0 is really intended to be used
> as integers in memory.

to me this would always be float in memory. since slope == 1 and != 0.

> To emphasize, there is currently no guarantee that an image will be
> identical if round tripped, and in general, it will not be identical
> now, if slope != 1 and intercept != 0.

what if scl_slope == 0, shouldn't we expect roundtrip identity?

I realize that the default change will use more memory, but I don't
> think we should be increasing the risk of silent generation of
> entirely wrong results in order to optimize memory, in the default
> case.

i agree, but is there a way to allow for keeping the datatype intact? are
we agreeing that a keyword is necessary, and dtype=None will keep the
original datatype.

> To improve the quality of the discussion - has anyone got an example
> of a real script that will give the wrong answer with the proposed
> change?

at least the common scripts we use won't give a wrong answer. but many of
our workflows will now crash because they would require additional memory
for specific pieces. now that's several layers embedded from a user point
of view.

is the proposed change the augmented proposal to include a dtype keyword?


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