[sane-devel] Weirdness with Canon FS2720U

[Gerald Murray]

Quoting Tabor Kelly <tkelly-sane-devel at taborandtashell.net>:

> What I would love for someone to take a look at is URB 289-300 in this 
> file 
>
(https://projects.cecs.pdx.edu/~kellyt/SANE-FS2720U/index.cgi/browser/sniffs/just_preview_color_negative_bw.LOG).
> 
>   It looks like the windows driver writes 24kB of data to the scanner. 
> But look at the data, it isn't firmware, it is a pretty pattern. Any 
> idea? Was the developer who wrote this driver just having a little fun 
> at my expense?

Hi,
I took a quick look at the urbs, and have seen similar transfers.  I do not
pretend to
be an expert in that area yet, as I have not reached coding phase for the
HP2400c
that I have been involved with.   This may not be a firmware upload.  For the
present
time I have been thinking that there are tables that are uploaded into a
scanner
for the purpose of gamma correction, and for shading tables at the point of
origin
of the data.  Some scanners obtain 48bits of data, but send only a smaller
number of
bits/pixel, such as 42, or 36.  A table could then alter the colors sent back.
Uwe posted some code like those urbs about July 5, 2006. 

regards,
Gerald