[sane-devel] Backend for plustek Opticbook 3600

Chris Berry s0457957 at sms.ed.ac.uk
Mon Mar 8 16:20:23 UTC 2010

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?



On 03/05/2010 07:26 PM, stef wrote:
> Le jeudi 4 mars 2010 17:13:12 Chris Berry, vous avez écrit :
>> On 03/03/2010 06:03 AM, stef wrote:
> ...
>> Ok thanks guys, this seems to have done the trick! There is now a black
>> line down one side of the page (not sure if that is supposed to be there
>> or not) and the colours seem to be a bit grainy. I have attached photos
>> to the site page
>> (http://sites.google.com/site/bez625/updates-1/update040310), these show
>> the shading calibration and the latest current scan.
>> If possible could you take a look and advise on how to sort out the
>> grainy parts of colour, im completely unsure myself :)
>> Chris
> 	Hello,
> 	I think there are a couple of things to look. First compute_coefficient()
> can't handle case where averaging is enabled for CCD, either disable averaging
> it or improve the function. Then you'll have to find what the offset to feed
> as a parameter. To find it I usually give 0 offset, then I count the number of
> vertical lines between a dark line and a bright one. Because a dark line isn't
> corrected and another is applied the correction which turns it bright. Then I
> use this value as offset. With some trial and error you can have a good value.
> You may also look at the color matrix.
> Regards,
> 	Stef

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