Re: SANE frames

Oliver Rauch (oliver.rauch@Wolfsburg.DE)
Sun, 22 Aug 1999 15:28:12 +0200

David Mosberger-Tang wrote:

> David> "If the frontend expects additional frames (e.g., the
> David> individual channels in of a red/green/blue image or multiple
> David> ^^^^^^^^^^^
> David> images), it can call sane_start() again."
> David> ^^^^^^
>
> PS: I think what's confusing in the SANE standard is the sentence that
> follows after the one quoted above. I changed it to read:
>
> Once all desired frames (and images) have been acquired, function
> \code{sane\_cancel()} must be called.

Hello David,

I think we have a problem here in the standard.

A frontend has to call sane_cancel when sane_read returns SANE_STATUS_EOF.

You say a backend can say I have more images and it does not use SANE_STATUS_EOF
in that case.
So: when the image is transfered completely and sane_read is called it is returns
with SANE_STATUS_GOOD instead of SANE_STATUS_EOF.

This way the frontend has to know when the image is transfered completly
because it can not call sane_read until it gets SANE_STATUS_EOF.

There is no problem with that as long as the frontend does know the size
of the image, but what about when the scan length is not known ?

Bye
Oliver

--
EMAIL: Oliver.Rauch@Wolfsburg.DE
WWW: http://www.wolfsburg.de/~rauch

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