[sane-devel] maximum image size for a scan for Canon pixma backend

Gernot Hassenpflug aikishugyo at gmail.com
Thu Dec 30 17:55:40 UTC 2010

On Fri, Dec 31, 2010 at 2:50 AM, Robert Krawitz <rlk at alum.mit.edu> wrote:
> On Fri, 31 Dec 2010 02:41:10 +0900, Gernot Hassenpflug wrote:
>> On Fri, Dec 31, 2010 at 2:19 AM, Gerard Klaver <gerard.klaver at xs4all.nl> wrote:
>>> On Fri, 2010-12-31 at 01:29 +0900, Gernot Hassenpflug wrote:
>>>> Dear all,
>>>> I have been involved in trying to support the Canoscan 9000F, and the
>>>> testing community has grown to about 15 individuals. A few of them
>>>> have programming knowledge and tonight one individual send in
>>>> corrected code to handle the final hurdle: correctly aligning the
>>>> sub-images in the 9600dpi TPU mode. So the scanner is now supported
>>>> for all modes.
>>>> However, for large images at both 4800dpi and 9600dpi modes, it seems
>>>> the max size of the image is limited in some way, so that only a
>>>> section of the desired image is delivered. Is this something that can
>>>> be set in the individual driver files (like pixma_mp150.c) or in some
>>>> of the generic pixma driver .c or .h files (which I do not want to
>>>> touch if possible)? I don't see a problem in the linesize or
>>>> dimensions, only in the image_size value seen by [pixma] debugging
>>>> output.
>>>> Best regards,
>>>> Gernot Hassenpflug
>>>> --
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>>> One possible solution (if not yet done), is to check the declaration of
>>> the  image_size parameter, for a 9600 dpi A4 scan (color) size is about
>>> 550 000 000 000 bytes. (long long is needed)
>> Hi, thank you for that. I see that image_size is currently declared as
>> "unsigned". I imagine that changing the declaration will need to be
>> checked in all places where the calculations using image_size are
>> done, or not?
>> Currently, from the report I obtain from a test user, a 4800x4800dpi image with
>> dimensions: 32824 px (width) * 47248 px (height)
>> should have a image_size of 4652605056 bytes (W*H*3 for channel number)
>> whereas the actual image_size used is 357637760 bytes (approximately
>> 341.1 MiB). I am still trying to ascertain whether for some reason the
>> wrong calculation for image_size might have been made, but certainly
>> the width and height are correctly there.
> 32824 * 47248 * 3 - 357637760 = 4294967296
> which is exactly 2^32.  So that suggests exactly the problem described
> above.

Ah! I suspected it was that, but forgot I had to take the difference
to get this number. Fantastic! Well, that sounds like somewhat of a
issue then for the SANE Canon maintainer to comment on. I guess this
issue had to come up eventually.

Gernot Hassenpflug

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