[sane-devel] genesys backend

[Pierre Willenbrock]

Hi,

Henning Meier-Geinitz schrieb:
> Hi,
> 
> Thanks for all your work!
> As far as I know, you use a LiDE 35. So i marked this scanner's
> support as "good". If you think the level of support is different,
> please change it in genesys.desc.
> 

It is working for me in daily use, so "good" seems to be okay.

> I tested a Canon LiDE 50. To get it running, I had to uncomment its
> id in genesys.conf. I changed this in CVS. I Also changed the name of
> the scanners to also show the Canon LiDE 40. Also I used a build
> number of 7, because the last one in CVS was already 6.
> 
> The test results for my Canon Lide 50:
> 
> Generelly: Sometimes I have a dark vertical stripe near the left
> border (about 1 cm width, over the complete image). This happens in
> Preview but very seldomly. Also I have vertical stripes, especially in
> medium-bright areas.
> 
> Color: 
> 75: Works, images are a bit too bright (over-imposed). Black
> looks grayish and some brighter colors are nearly white.
> 

Seems like the shading calibration does not work correctly for you.
Grayish black is okay, i don't want to cut the color range. But brighter
colors getting near white is not.

When using SANE_DEBUG_GENESYS=255 there should be an image named
"black_white_shading.pnm" in the current working directory. It contains
a scan of the calibration area. Please send it to me.

> 150: Sometimes works, most of the time the scan hangs at about 95%.
> I.e. there is a normal scan but the scan head stops and xsane never
> displays the image. Also tested with scanimage. When it works, the
> image looks like at 75 dpi. The problem depends on image width. E.g.
> at a width of 20 mm, it always works at 150 dpi but not with the full
> width. Sledomly, I also get a segmentation fault.
> 

Mine does not expose such behaviour. Could you please send a complete
log with SANE_DEBUG_GENESYS=255 and SANE_DEBUG_GENESYS_GL841=255?
I already see one problem: The result of "genesys_fill_read_buffer"
really should not be ignored.

> The log shows that this part is repeated endlessly in case of a freeze:
[log]
> 
> After the freeze or segmentation fault, the scanner is sometimes not found
> anymore. Replugging fixes that.
> 
> 300, 600 dpi: Works (overimposed) in full width. Doesn't work at e.g. width
> 100 mm (see above).
> 
> 1200 dpi: Doesn't work in full width (see above). Works at e.g. a
> width of 20 mm. This is much darker and has vertical stripes
> (calibration problem?)
> 
> 2400 dpi: Same as 1200 dpi. In addition, the image is too long (factor
> 2). I.e., in modes like 1200x2400 dpi the x resolution must be
> "inflated" by either just duplicating pixels or, better yet,
> interpolating them.
> 

I must admit that i never tested 2400dpi. But looking at my logs, i see
that scanimage requests 1200x2400dpi, and we are delivering that. So,
the correct behaviour if we get different resolutions for x and y is to
use them internally, and interpolate to create an image with the maximum
 of x and y resolution(2400dpi in that case)?

> Gray:
> 75 dpi: Works, but is over-imposed.
> 150-600: see color
> 1200, 2400: see color 1200/2400
> 
> Lineart: similar to gray
> 
> I also did a spot check on color 16 bit and this seems to be less
> over-imposed.

16 bit doesn't use any gamma. For 8 bit there is a gamma of 2.2 or
0.4(don't remember which one), which should match what Canon does(at
least i am sending a very similar gamma table).

Thanks for your testing.

Regards,
  Pierre