[sane-devel] Bug in snapscan or sane network protocolo?

[Henning Meier-Geinitz]

Hi,

On Thu, Jun 09, 2005 at 04:47:05PM +0200, Giuseppe Sacco wrote:
> Basically I do a scan of 210.0x297.0mm, using a 200dpi resolution.
> Prior to scan I call get_parameters and receive an *estimated* values
> for lines, pixelsperline, bytesperline; after receiving this data I
> receive the frame data.

Which frontend do you use?

> while, when scanning, I get a different amount of data:

This is perfectly legal (see SANE standard). The normal way is:

sane_get_parameters (returns estimated values)
sane_start
sane_get_parameters (returns exact parameters)
--> malloc memory for image, ...

> I see two possible options:
> 
> 1. Change the snapscan algorithm to have better supposed values

If snapscan doesn't return the correct parameters after sane_start,
it's broken. But I'd be very surprised if that were the case as that
would break all frontends.

> 2. Change the sane network protocol in order to get all corrected
>    parameter *with* or *after* the scanned data.

I haven't checked that but you can get the parameters after running
sane_start, can't you?

You can test the behaviour of frontends concerning the estimated
parameters with the "test" backend (use option "fuzzy parameters").

Bye,
  Henning