2009/10/21 Stéfan van der Walt <stefan@sun.ac.za>

2009/10/21 Ralf Gommers <ralf.gommers@googlemail.com>:
> There is a dtype argument already, you merged my patch for that, commit
> 44679c7aae5d6b3747c88d46756a3dc96c9a727f.

Oh yes, of course :)

My point remains, however, that the default for dtype may have to be
changed for consistency.

Don't think I would agree with that. dtype=None is consistent with how NumPy does this. See for example np.array / np.asarray. 

 Currently, you have to read the docs to
figure out what type will be returned, and I feel that element of
surprise can be eliminated simply by specifying the default
dtype=float or dtype=np.uint8.

The returned type by default is the type the image was saved as. To me that is the only thing that makes sense.

The only thing you have to look up in the docs is what dtype you get when specifying flatten=True. Since you explicitly ask for color -> grey-scale conversion, a sensible type has to be chosen if it's not specified. The smallest type that makes sense is float32.