[sane-devel] Epson perfection 660 usb - problem with lineart scanning - snapscan backend

[Oliver Schwartz]

Hi,

> > When I try to scan in lineart mode, it makes garbage on output.
> > The scan seems "misaligned".
> > But if I first make a scan in gray or color mode, and then switch
> > to lineart, it works !
>
> It works ... sometimes :(
>
> I acquire a scan in Lineart mode and make a log :
> http://www.starox.org/pub/sane/snapscan/lineart.log
> It makes dirty squares in the image :
> http://www.starox.org/pub/sane/snapscan/lineart.pnm

So... is this the best result you can get or does it work ok (without 
the dirty squares) if you scan in grayscale first?

Unfortunately it seems that lineart mode is less and less supported in 
newer scanners. These scanners always scan in grayscale mode, the 
conversion to lineart has to be done in the backend. I don't know if 
this is the case for the Perfection 660, but on the other hand 
there's not much that can fail on lineart mode. 

Maybe you can provide an USB trace of a lineart scan on windows. 
You need to install an USB sniffer first. I prefer USBSnoop which is 
available from http://benoit.papillault.free.fr/usbsnoop/ . The page 
also gives basic instructions on how to use it.

To produce the log you should
- unplug and replug the scanner
- Start the scanning software
- Do a preview scan
- Do a very small scan with lowest resolution

You can send the (compressed) log to me in private mail

/Oliver