Update unscaling to use the per-band scale/offset values

[jddeal]

Hey there!

This is a small change to extend unscale=True to lean on the per-band values instead of assuming the first scale/offset applies to all bands.

(Sponsored by Vaisala Xweather)

[jddeal]

I suspect we might have a rather uncommon use case, but we haven't run into any limitations through gdal or rasterio that would imply only one scale/offset should be set per file.

Some example docs:

• gdal_edit.py will set either one value for all bands or per-band values
• rasterio DatasetReader returns per-band values

[four43]

@jddeal I'm not quite sure why we need this. In GDAL/Rasterio I thought the metadata model was to have only one scale/offset value 🤷‍♂️

I will be forever sad that the nodata value is applied per file, not per band anymore. That's such a shame for heterogeneous data :(

[vincentsarago]

@jddeal I don't seems to have push right on the fork so I cannot edit this PR

[vincentsarago]

Suggested change

	scales = numpy.array(dataset.scales).reshape((-1,) + (1,) * (len(data.shape[1:])))
	offsets = numpy.array(dataset.offsets).reshape((-1,) + (1,) * (len(data.shape[1:])))
	scales = numpy.array(dataset.scales).reshape(-1, 1, 1)
	offsets = numpy.array(dataset.offsets).reshape(-1, 1, 1)

should be enough, I don't see rasterio handling non 2D data

[vincentsarago]

edited in #708