I feel it's a bit stupid and confusing to call it the alpha channel.
Alpha channel has a very well defined and established meaning in the
graphics world. Just because you can dump the infrared data into the
4th channel of a file doesn't make this data 'alpha' in any way. If
you look at the SANE standard, it defines the red channel as 'data
from the red spectral band', etc. , so why would the infrared channel
be treated differently.
Should scanners in the future support a different sort of 4th channel,
lets say height, then it should get it's own SANE_FRAME name (eg RGBH
The SANE_FRAME name tells the frontend what sort of data it is that it
receives. Perhaps your frontend isn't interested in this but other
-- -- Ewald
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