[sane-devel] Canon LiDE 200 scanning fails with backends from PPA

[stef]

Le Monday 25 April 2011 22:17:46 Martin Ueding, vous avez écrit :
> Dear Stef,
> 
> I tried your command, it did not work the first time, the second time
> returned a reasonable looking image.
> 
> First try:
> 
> 	$ scanimage -d genesys --resolution 100 --mode Color > scan100dpi.pnm
> 	scanimage: sane_start: Error during device I/O
> 
> Second try:
> 
> 	$ scanimage -d genesys --resolution 100 --mode Color >scan100dpi.pnm
> 	# no output
> 
> The [image](http://img851.imageshack.us/img851/7334/scan100.jpg) looks
> good to me.
> 
> 
> When I tried to scan an A4 document, it worked on the third try. And the
> scanner seemed slower to me. Additionally, it made some strange noises
> that sounded like the head would move in two directions at once. The
> error was the same “Error during device I/O”.
> 
> The image quality seems lower than the results that I got with Canon's
> MP Navigator EX 2.0 on Mac OS X 10.5 before. I there used 200 DPI,
> grayscale and textdocument as a source, writing a JPEG. Now I used
> 
> 	scanimage --mode Gray -x 210 -y 297 --resolution 200
> 
> and the [result](http://img708.imageshack.us/img708/8666/10543314.jpg)
> does not look too good.
> 
> 
> This is better than before, but the I/O errors are still strange. Is
> there anything else, that I can do about that?
> 
> 
> Martin
> 
	Hello,

	this scanner is based on a GL847 which has no native support for image 
sensor built from several sensors. In the LiDE 100/200 case, the backend must 
scan internally all the scanarea width to give the correct picture. This 
involves the transfer of big amount of data on USB. So these scanners are 
often affected by 'backtracking' where the scanner has to go back while 
waiting for scanned data to be transfer to the host. It may even fail. I am 
currently reworking this part of the backend to bring 2400/4800 dpi for LiDE 
200. I expect it will help this case.
 
	Concerning the image quality, MP Navigator EX 2.0 scans at least at 300 
dpi then process the data. You may do the same. By using 'xsane' you'd be able 
to tune the quality more precisely and easily than by using 'scanimage' or 
'simplescan'.

	Now scanimage is working, can you try 'simplescan' again ?

Regards,
	Stef