[sane-devel] Problems with Canon MP990 transparency unit

[Guillaume Courtois]

Hi guys,

I'm currently trying to make the TPU correctly work on my MP990 scanner. 
It seems like there are shifting problems both in datas and in the 3 
colors (which seem to be 2 separate issues, but not sure).

I'm currently testing on my debian SID with sane GIT version, but I have 
tested packages from SID and made tests on a Mint 17 netbook also. All 
seem to give the same results.

It seems like datas are not shifted in 300 dpi but are more and more 
shifted when you choose higher resolutions (600, 1200, 2400 dpi).

I'm happy to provide pictures if you want to see what it gives, but that 
gives vertical black stripes on the captured picture.

Here is the output of xscanimage with some debug activated :

Here is the 300 dpi correct scan :

[pixma] pixma_scan(): start
[pixma]   line_size=3378 image_size=9674592 channels=3 depth=16
[pixma] Reader task id=140539733346048 (threaded)
[pixma]   dpi=300x300 offset=(780,88) dimension=563x2864
[pixma]   gamma_table=0xd939e0 source=2
[pixma]   threshold=127 threshold_curve=0
[pixma]   ADF page count: 0
[pixma] Setting non-blocking mode
[pixma] Current status: paper=0 cal=0 lamp=2 busy=0
[pixma] Current status: paper=0 cal=0 lamp=2 busy=0
[pixma] Current status: paper=0 cal=0 lamp=2 busy=0
[pixma] Lamp status: 3 , timeout in: 19
[pixma] pixma_read_image():completed
[pixma] Reader task terminated
[pixma] Reader task started
[pixma] Reader task id=140539733346048 (threaded)

Here is the not-so-correct 1200 dpi scan :

[pixma] pixma_scan(): start
[pixma]   line_size=13938 image_size=67376292 channels=3 depth=16
[pixma]   dpi=1200x1200 offset=(282,446) dimension=2323x4834
[pixma]   gamma_table=0xd939e0 source=2
[pixma]   threshold=127 threshold_curve=0
[pixma]   ADF page count: 0
[pixma] Setting non-blocking mode
[pixma] Current status: paper=0 cal=0 lamp=2 busy=0
[pixma] Current status: paper=0 cal=0 lamp=2 busy=0
[pixma] Current status: paper=0 cal=0 lamp=2 busy=0
[pixma] Lamp status: 3 , timeout in: 19
[pixma] WARNING:image size mismatches
[pixma]     67376292 expected (4834 lines) but 44044080 received (3160 
lines)
[pixma] pixma_read_image(): completed (underrun detected)

As you can see, mismatch and underrun tells me I have to dig around 
that.

Also, it seems like data coming from the preview window is 
mis-interpreted : I have to pick a smaller and decaled window in order 
to get the actual correct part of the scan I want to have (I don't know 
if I'm pretty clear on that one ?).

I'm still digging into the code to see if I can correct that but if you 
guys could point me to the right direction, that would save me lots of 
time.

Thanks for your attention, keep up the nice work on sane !

Bye.