[sane-devel] Proposal: SANE standard addition

abel deuring a.deuring@satzbau-gmbh.de
Sun, 29 Sep 2002 18:30:15 +0200

Henning Meier-Geinitz wrote:
> Hi,
> On Sun, Sep 29, 2002 at 12:24:21PM +0200, Oliver Rauch wrote:
>>I think this is ok. I suggest to add a sentence that this transfermode
>>is not used very often and the backend author should be aware
>>that not all frontends may support this mode.
> Ok, I'll add a paragraph at the end of the section:
> | In frames of type SANE_FRAME_GRAY, when the bit depth is 1 there are
> | only two sample values possible, 1 represents minimum intensity
> | (black) and 0 represents maximum intensity (white). For all other bit
> | depth and frame type combinations, a sample value of 0 represents
> | minimum intensity and larger values represent increasing intensity. 
> "The combination of bit depth 1 and SANE_FRAME_RGB (or SANE_FRAME_RED,
> SANE_FRAME_GREEN, SANE_FRAME_BLUE) is rarely used and may not be
> supported by every frontend."

I'm afraid that this could lead to increased traffic on this list. If we 
have a backend for a more popular scanner which supports 1 bit RGB 
output, we will probably get a number of questions, what some strange 
error message means or why the output look scrambled. As a workaround, 
the frontends should at least be be able to display a message "this 
program does not support 1 bit RGB scans.", if a user attempts to start 
such a scan.

For Sane 1, we can probably live with this inconsistency -- but for Sane 
2, we should either omit the 1 bit RGB mode completely (which I would 
not like that much...), or all frontends should support all "basic" data 
formats. Alternatively, we would need something like "content type 
negotiation protocol" which would allow a backend to enable only those 
options, which lead to scan modes supported by the frontend.