# 16 bit per sample support

Oliver Rauch (oliver.rauch@Wolfsburg.DE)
Sat, 13 Mar 1999 10:39:17 +0100

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Hi,

*** TO ALL BACKEND AUTHORS, PLEASE READ THIS ***

I want to include a 16 bit per sample support for xsane.

But there are some things I need to know before.

We need a well known option so the frontend can select 8 bit/sample
for preview or phtocopy and so on. It does not make sense to do a
preview or a photocopy with 16 bits per sample and I don't like to
write a 16 to 8 bit conversion so it would be great if we could define
such a common option for all backends.

We could define an option the way like the preview option is defined:
SANE_TRUE=> backend sends not more than 8 bit/sample
SANE_FALSE=> backend can send more than 8 bits/sample
or we define an option bit_depht that must be a SANE_CONSTRAINT_WORD_LIST
so the frontend can simply select "8" (if available) for preview and so on!

In the sane api it is not define how bit depths between 8 and 16 bits are
handled.
So if the scanner gives back 12 bpp is this bit 0-11 or bit 5-16 or does this
mean
the colors are mixed togeht in some bytes:
(8 bits red) (4 bits red, 4 bits green) (8 bits green) (8 bits blue) (4 bits
blue, whats with the rest?)

How can the fronten find out how the backend does this?
Is it ok for a backend to say it is 16 bpp and use bit 5-16 although it is only
12 bpp ?

I think we need a closer definition about that!
David, any suggestions?

Bye

Oliver

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