Relax channel restrictions on IBA::resize, fit, resample. (#2125)
Relax channel restrictions on IBA::resize, fit, resample. (#2125)

They had previously outright rejected if the destination and source
images didn't have the same number of channels.

But actually, it doesn't matter. If they differ, it will only operate on
the minimum channel count in the two images. If dst has more channels
than src, that's fine, it just won't fill in the "missing" channels.  If
dst has fewer channels than src, then that's also fine, and in fact it
is totally reasonable to want to resize an RGBA image into an RGB
buffer, resizing while only copying the first 3 channels.
OpenImageIO/oiio,OpenImageIO/oiio,lgritz/oiio,lgritz/oiio,OpenImageIO/oiio,lgritz/oiio,lgritz/oiio,OpenImageIO/oiio