[sane-devel] Backend for plustek Opticbook 3600

[Chris Berry]

On 02/12/2010 08:47 AM, stef wrote:
> Le jeudi 11 février 2010 19:50:25, vous avez écrit :
>    
>>> 	Hello,
>>>
>>> 	I am facing the same issues than you while adding support for the
>>> HP3670. I eventually found that one of my decoding script was buggy and
>>> hide most of AFE accesses. I have appended the fixed version. By decoding
>>> usbsnoop again, you may find more AFE writes to be coded in backend. That
>>> may fix the red tint issue you have. I wouldn't be surprised if only
>>> write to red gain was showing in decoded log, leaving other channels
>>> untouched.
>>>        
>> Ok I have decoded another log file using this revision, you are correct
>> there are many more writes to the fe showing up but they do not really
>> mean anything more to me :(. I have attached the fe_writes.log file,
>> which is just a straight grep of the fe writes with the new decoded log
>> file. If you could look at it and tell me what you think is happening,
>> the only reasonable things I can gather is that there are:
>>
>> * init style writes (0x00 ->  0x70, 0x01 ->  0x80, everything else ->  0x00)
>> * possible offset settings (0x05-0x07 seem to be set to 0x80 and 0xff
>> repeatedly)
>> * offset (0x05-0x07) and gain (0x02-0x04) seem to be set arbitrarily at
>> various times.
>>
>> I'm not sure if any of this is relevant but whenever I set the
>> offset/gain values in genesys_devices they seem to make little (if any)
>> difference to the scans.
>>
>>      
>>> 	You'll also have to look at the base gamma coefficient in the
>>> Genesys_Sensor entry for your model.
>>>        
>> I've had a look at this and I take it you mean this section:
>>     float red_gamma;
>>     float green_gamma;
>>     float blue_gamma;
>>     uint16_t *red_gamma_table;
>>     uint16_t *green_gamma_table;
>>     uint16_t *blue_gamma_table;
>>
>> I've tried changing the floats but there doesn't seem to be much
>> difference, maybe I should wait until I fix the shading issue then tweak
>> this?
>>
>> I assume the gamma_table entries are just initialisers for the tables.
>>
>>      
>>> 	When doing a calibrated scan, the REG01_DVDSET bit is set to activate
>>> shading calibration. Clearing it may side step issues with shading
>>> calibration, but defeat the purpose of calibration.
>>>        
>> I was slightly worried that's what I had done here, i've restored it to
>> the original values :P
>>
>>      
>>> When tuning shading calibration, you must
>>> look at the black/white_shading.pnm and black/white_average pnm files
>>> that are written when full debug is enabled. With proper offset and gain
>>> values, you must have a full black picture (with some values slightly
>>> above 0) and a full white one. If not, the computed shading calibration
>>> coefficient will be bogus and you'll get black scans.
>>>
>>> Regards,
>>> 	Ste
>>>        
>> Ok i've also attached the black/white_shading/average files. If I
>> understood you correctly the black_shading.pnm should be all white and
>> not the pretty purple colour it is now and conversely the white should
>> not look as it does. I have tried altering the offset and gain in
>> gen_devices but this doesnt seem to do anything :(. Any other
>> suggestions about how I move forward with the shading? I think as soon
>> as the shading is sorted I might be there with this project and ready to
>> commit to the dev version.
>>
>> Also I currently have OFFSET_CALIBRATION and DARK_CALIBRATION flags set
>> for the scanner, how do I know if I should be using these (as opposed to
>> COARSE_CALIB and DARK_WHITE_CALIB)?
>>
>> Sorry I have given you quite an essay to read there but at the minute I
>> have a few assignments to deal with so i'm just trying to juggle
>> everything but again thanks for all the help and time you have given me.
>> One other thing I wanted to ask is about a new release? I've seen a lot
>> of chat on the mailing list about this but I just wondered if you knew
>> any more specifics?
>>
>> I only ask because I am taking this project on as part of my University
>> course and the ideal end result for me is to have the drivers present in
>> a SANE stable release,so if I could do this by the next release that
>> would be perfect :)
>>
>> Thanks
>>
>> Chris
>>
>>      
> 	Hello,
>
> 	regarding the AFE writes, judging by the AD9826 data sheet the writes to
> addresses 0x02-0x04 are R, G and B gains. The interesting thing is that red
> gain value 0x32 is higher than the 2 others (0x1e). So a red tint seems
> sensible. Personally, I would try to set them all to 0x32 (preferably) or 0x1e
> and map the gain array to these addresses. The other writes at 0x05, 0x06 and
> 0x07 are for offsets. For instance the sequence of AFE writes matches it, wee
> see gains set to 0 and various offsets tried. Then gains are set half range
> (0x80) and new offsets are tried. Looks like offset calibration for me. The 2
> remaining addresses are for AFE configuration.
>
> 	For shading calibration, GENESYS_FLAG_DARK_WHITE_CALIBRATION would allow do
> calibrate in one pass and generate 'black' data using dark areas. To my
> opinion, GL842 scanners need really good black data to do proper shading
> calibration, so I'd recommend using the GENESYS_FLAG_DARK_CALIBRATION flag
> instead. Once gains are good, you'll have a better reference white scan. But
> the white_shading.pnm shows there is a black line in the scanned area.
> Scanners have often different calibration area (located under the roof, can be
> seen by disassembling the scanner, or doing an uncalibrated scan with 0 y
> offset in genesys_devices struct). While the packaging may slightly vary from
> one model to another, this black line is always at the same distance from the
> scanning area. See GENESYS_FLAG_SEARCH_START flag. It also 'tells' where the
> white calibration is located. You'll have to get sure that the shading
> calibration scan only a white area.
>
> 	One more model supported in the stable release would be a nice thing indeed.
>
> Regards,
> 	Stef
>
>    

Hey Stef,

Sorry I haven't been in touch in a while I have been busy. Ok i've 
looked at this and my understanding is that I have to do two things; 
sort the gain values out and the shading calibration. For the time being 
i am disabling the shading until i have the correct gain values for my 
scans, my understanding is that it will be easier to correct the shading 
once the gain is fixed.

After trying some different values I find that altering both the gain 
and the gamma colours in the Genesys_sensor has an affect on the 
scanning image. My question is how do I find the correct values for 
them? When i take the fe values for the gain from a snoop they are way 
off, and i dont think i can counter this with the gamma values.

Also do you know when a next release is likely to happen? Just need to 
know if I have to hurry up with this as i'd like to have it ready for 
the next one.

Thanks

Chris

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