Lower the default number of bins

[thewtex]

256 makes computation very slow, and this is larger than the typical number of effective intensity bins encountered in many images. A better default is 8, 10, 16?

[blowekamp]

Related is the default range of the histogram. This defaults to the range of input pixel type. I think that reducing the size of the histogram may result in the all the intensities being in one bin for some common medical image modalities. Without adding a feature of automatically detecting the min/max of the input, it is risking producing constant images by default.

So I think this is a good idea. Along with adding a feature request for auto-range detection by default.