[sane-devel] Backend for plustek Opticbook 3600

Chris Berry s0457957 at sms.ed.ac.uk
Tue Mar 16 19:02:33 UTC 2010

On 03/09/2010 05:15 AM, stef wrote:
> Le lundi 8 mars 2010 17:20:23 Chris Berry, vous avez écrit :
>> Ok Stef I have a bit more time to concentrate on this at the minute. I
>> have updated the white_shading.pnm and included it at
>> http://sites.google.com/site/bez625/updates-1/update080310 there is also
>> a copy of the latest scan there too. I only have 20 shading lines in the
>> shading area because there is a lot of blue in that area. Should I widen
>> it (more shading lines) or should those blue areas be included?
>> Also how do I disable the averaging? Is it a software thing or is it on
>> one of the registers? I'm also not too sure what you mean about the
>> offset, is it the DAC offset?
>> Thanks
>> Chris
> 	Hello,
> 	the white shading picture must be all white. The picture you posted is mostly
> OK, but there is still some blue on the right. This is not a blocker, but it
> will certainly have to be fixed to reach best image quality.
> 	By averaging, I was thinking of the AVEENB bit of register 3 which tells the
> ASIC to delete extra data points or average them to produce data from higher
> dpi.
> Regards,
> 	Stef
Hey guys,

I have experimented with disabling average and altering the offset as 
Stef suggested. Disabling averaging seems to make things worse (dark and 
light lines where solid colour appears with AVEENB) and changing the 
offset seems to make no real difference so i'm not sure what is 
happening. Also I am unsure about what target code I should use for the 
shading compute_coefficients (assumed 0xdc00 as it seems popular).

At the project site (update ) there are a few images in a bzip file to 
show what I mean about toggling the AVEENB. It certainly seems better to 
have it on but this might just be misleading images.

The main issue now seems to be the different coloured vertical lines 
down the document. In addition I performed higer dpi scans (300, 600) 
and the whole image seems darker and the vertical lines are more 
prominent, i cant say im entirely sure whats causing them but im 
guessing its the shading function.

I have also attached my source on the project update if this will make 
it easier to advise on what im doing wrong. I will get around to tidying 
up my code soon so i can commit to git without it looking messy. Has 
there been anymore information about a next release date? I have been 
skimming the mailing list and not seen anything mentioned.


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