[sane-devel] Canon LiDE 90

[Guillaume Gastebois]

Hello,

Pierre Willenbrock a écrit :
> Hi Guillaume,
> 
> Guillaume Gastebois schrieb:
>> Hello,
>>
>> Why calibration is so long (~50/60s) ?
> 
> It is probably failing. Should take about 3-5 seconds. Look at the logs,
> the calculated averages and calibration are dumped there.
> 
>> What are /* Start of white strip in mm (y) */ and /* Start of black mark 
>> in mm (x) */ in genesys_devices.c ?
> 
> Those are configuration values for calibration steps. I don't know if
> any of these are currently used or if the values are hardcoded.
> 
> I think the start-of-black-mark is used to detect the beginning of the
> document area for some gl646 scanners. The start-of-white-strip was once
> used in shading calibration. Currently, the shading calibration is setup
> for a calibration area looking like this:
> 
> home position
> +--------------------------------
> !   black area
> +--------------------------------
> !   white area
> +--------------------------------
> 
> The border between black area and white area is autodetected per pixel,
> as the border is usually not straight.
> 
> You scanner seems to offer only a white area, so we will need to do
> shading calibration differently. My current idea is this:
> * always gather data on a white area
> * for black data, reduce the led exposure time to the minimum(0x101,
> those registers cannot be set to 0. per byte.).
> * for white data, use the normal exposure times
> I tried something like this for offset calibration, to see if there is
> any difference between white area+0x101 exposure time and black
> area+normal exposure time. There was no difference in the final images,
> and i think the resulting calibration was the same as well.
> 
>> Regarding the log file you said :
>> W  ! 0x23 ! 0x050 ! dac value rgb(offset value)
>> W  ! 0x2b ! 0x028 ! pga gain rgb
>> But on debug, I see that these two registers are never written.
> 
> 0x23 and 0x2b are merely convenience registers. Writing to 0x23 and 0x2b
> is equivalent to a write to each of 0x20-0x22 and 0x28-0x2a. For
> cis-sensors, there is only one channel used, so we could get away with
> only two registers writes(for the correct channel or 0x23/0x2b), but
> this won't work for ccd-sensors.
> 
>> Another thing : when scaning in color the leds are blue ????
> 
> I'd expect a shade of white, perhaps blueish. my scanner does a
> magentaish white. You may also see the single colors when quickly moving
> your eyes relatively to the scanner.
> 

Yes, I know that. But I only see blue and green. No red.....

> Regards,
>   Pierre
> 
>
Regards
Guillaume