[sane-devel] High DPi Scan using Ubuntu 18.04.3

[r. a. schmied]

Povilas Kanapickas wrote:
> Hi,
> 
> On 1/4/20 7:21 PM, Ralph Little wrote:
> 
>>Hi,
>>
>>On 2020-01-01 11:13 a.m., Sotirios Giavis wrote:
>>
>>>I want to scan an area of 50 x 50 mm at 4800 dpi in full-colour 16 bits.
>>>This should be possible with Canon Lide 210 but my system won't.
>>>
>>
>>I confirmed the specifications of the scanner that it should indeed be
>>optically capable of 4800dpi.
>>I have one of these scanners and I just tried it out. Indeed, in Sane
>>1.0.28, 4800dpi is not currently supported and scanning is dropped down
>>to 2400dpi.
>>
>>Looking at the code of the Genesys backend, I see this:
>>
>>    model.resolutions = {
>>        {
>>            { ScanMethod::FLATBED },
>>            // BUG: 4800 resolution crashes
>>            { /*4800,*/ 2400, 1200, 600, /* 400,*/ 300, 150, 100, 75 },
>>            { /*4800,*/ 2400, 1200, 600, /* 400,*/ 300, 150, 100, 75 },
>>        }
>>    };
>>
>>
>>That suggests that it should be supported but is buggy at the moment.
>>If I have time this weekend, I will look into it.
> 
> 
> I've already checked this issue and it seems to be some weird
> interaction within the backend. The high-resolution setting does not
> just crash, it produces noise. I suspect that somewhere we break the
> pixel order, but haven't tried to investigate it yet.
> 
> Regards,
> Povilas
> 
> 
> 
> 
Povilas and other interested saners

using an early 1.0.28 version with hacks for solaris 10; primarily for the
old old libusb provided with that os, along with a canoscan lide200 all the
high resolution settings (eg 4800, 2400, 1200) will generate correct 16bit
.pnm image data if a 16 bit png lib is used and the image display also uses
the 16 bit png lib.

in my situation only imagemagic display 7.0.8-29 Q16 sparc 2019-03-04
correctly displays hi-res 16bit pnm images.  8-bit images of any res
are no problem with xv, xzgv and display.

hope this helps with your investigation, but note the lide200 is the
genesys gl847 stuff and not the gl124 that is used for the lide210.

aloha

ras

ps -- happy new year to all -- ras