Image data types and conversions

[Andreas Mueller]

Hi Stefan.

> Accuracy is definitely #1.  That's why the suggestion is that
> algorithms choose for themselves.  Sometimes it makes sense to return
> the same type as the input, sometimes it doesn't.  What is important
> is that images remain scaled, and can again be interpreted by the next
> function in the pipeline.  Where possible, we do not want to make
> copies in memory.  So, in rgb2gray's case, e.g., the conversion gives
> floating point numbers by default.  We do not need to convert those
> numbers to uint for the user and, actually, we shouldn't--because that
> would destroy accuracy.
>

Thanks. That definitely answers my question.

> I'll whip up the conversion functions and offer them as a PR.  This is
> probably important, since it will influence the code written for 0.4 a
> lot.
>
Thanks for tanking my concern seriously. Sounds great :)

Cheers,
Andy