[sane-devel] Well known option consensus

[abel deuring]

m. allan noah wrote:

>> > But back to the problem I have/had with Etienne's suggstion for the
>> > "relations" between page size and scan window coordinates: It does
>> > not make much sense to allow to set a scan window in overscan mode:
>> > The backend should calculate the scan window settings automatically
>> > from the page size, and disable the options tl-x, tl-y, br-x, br-y.
>>
>> No ! If a user want to scan only a portion of the paper, he must be able
>> to set scan area, but as long as there is no scan surface, we use paper
>> size as scan surface. That make sense !
> 
> you missed the point here. we are talking about an overscan option, which
> causes the scanner to add space all around the scan, such that the back-
> ground shows thru.
> 
> but i think a person might want to overscan and still have only a
> small area of the page (one of the corners?) i think i can work this
> out, and still be compatible with the text of our suggestion.

Since the "level" of page size and skew detection is quite low in
the scanners we're talking about, I think a backend does not need to
do much here: In overscan mode, the backend simply returns the image
of the document surrounded by "easily distinguishable", typically
"dark" pixels; it is up to the frontend to detect the page borders
and rotation angle.

All this does not mean that the frontend cannot let the user select
a smaller scan window within the page area -- but the clipping of
the image must be done by the frontend.

Abel