Pls don't make it your last comment, at least until we all understand
how it is MEANT to work :-)
mh wrote:
>
> Mick Barry, Don, 01 Mär 2001 :
> > Tom,
> >
> > Thanks muchly for this.
> >
> > I'm still unclear on how a f/e knows that there is new image, and not
> > just a new frame for the current image. Is it implied by what frames
> > have been recieved.
> > So if we looked at just the getparameter replies is the following how it
> > is intended to work:
> >
> > GetParameters (format=Red, LastFrame=false)
> > GetParameters (format=Green, LastFrame=false)
> > GetParameters (format=Blue, LastFrame=false)
> > // Implies a new image cause we've already read r, g & b
> > GetParameters (format=Grey, LastFrame=false)
> > // Implies a new image cause we've read grey image which only has simple
> > frame
> > GetParameters (format=RGB, LastFrame=false)
> > // Implies a new image cause we've read rgb image which only has simple
> > frame
>
> Hi,
> ok, I hope, one last comment is allowed (and please correct me, if I'm wrong):
>
> According to the current SANE Standard, there's absolutely no way for a frontend
> to determine, whether there's another image available, especially not by
> a call to sane_get_parameters().
> The member last_frame is *always* false, if your scanning a single frame image
> (like RGB or grayscale). This member is only used if you are scanning a
> multi frame image.
> See SANE Standard 1.02, page 28:
>
> "Member last_frame is set to SANE_TRUE if and only if the frame that is
> currently being acquired (or the frame that will be acquired next if there is
> no current frame) is the last frame of a multi frame image (e.g., the current
> frame is the blue component of a red, green, blue image)."
>
> There is no "well known option" or a flag in SANE_Parameters which tells the
> frontend that it should continue with image acquisition. Therefore you
> have the following possibilities:
> -let the user hit the scan button for each single scan operation
> -let the user set the number of scans, and then try to acquire this number of
> scans.
>
> ...as I said before, please correct me, if I'm wrong.
>
> Michael
>
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