[sane-devel] High DPi Scan using Ubuntu 18.04.3

[Povilas Kanapickas]

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