[sane-devel] Colour problem with Canon Maxify MB5150

[Dr Rainer Woitok]

Ralph,

On Wednesday, 2021-05-19 18:21:57 -0700, you wrote:

> ...
> On 2021-05-19 8:46 a.m., Dr Rainer Woitok wrote:
> > ...
> >   - The PNG file from the flatbed clearly showed the original paper hav-
> >     ing been rather thin, since some colours from the reverse side shone
> >     slightly through, and the background colour having been faintly grey
> >     rather than white.   In other words, this PNG file was a fairly good
> >     copy of the original.
> >
> >   - But the PNG file from the ADF did show almost no shine through and a
> >     more or less purely white background.  Dark colours appeared slight-
> >     ly darker and light colours slightly lighter than the original.  The
> >     effect was somewhat similar to using ImageMagick's "-normalize" opt-
> >     ion.
> > ...
> Some of the pixma devices seems to have a completely different engine
> for generating scans from the ADF compared to the flatbed.
> For ADF, they return JPEG data to SANE instead of the normal raster data
> that we get from flatbed.
> I have no idea why that would be the case but they do use the same sensors.

I have meanwhile opened a support case with Canon  complaining about the
low quality of ADF scans.   In their response Canon pointed out that ADF
(at least normally) is optimized for speed rather than quality and sugg-
ested testing with  "IJ Scan Utility"  using the various settings of the
"Advanced Mode" provided by "ScanGear".   So I reanimated my old Windows
Vista laptop,  installed "IJ Scan Utility" from the Canon CD and started
it.

I selected "Document (ADF Simplex)", "A4",  and "Color" in the input and
"300 dpi" in the output section,  and under "Image Settings" I left "Im-
age Adjustment" at "Document"  and set "Unsharp Mask"  and "Descreen" to
"OFF" and "Reduce Dust and Scratches"  and "Grain Corretcion" to "None".
Hitting "Scan" I eventually obtained file "ScanGear-ADF-Doc.png".

In the second run I just changed  "Image Adjustment" to "None" (the only
alternative offered) and scanned to file "ScanGear-ADF-None.png".

Finally,  I changed the Source to "Platen"  which forced "Paper Size" to
"Full Platen"  and "Image Adjustment" to "None"  (greying both out), and
received file "ScanGear-Flatbed.png".

Here are the file sizes:

   $ ls -l ScanGear-*
   -rwx------ 1 rainer rainer  3324661 2021-06-29 15:48 ScanGear-ADF-Doc.png
   -rwx------ 1 rainer rainer 11142577 2021-06-29 15:49 ScanGear-ADF-None.png
   -rwx------ 1 rainer rainer 15357308 2021-06-29 15:49 ScanGear-Flatbed.png
   $

Files "ScanGear-ADF-Doc.png"  and "ScanGear-Flatbed.png"  are similar in
size and quality to the files I originally obtained using "scanimage" on
Linux,  while the quality of file  "ScanGear-ADF-None.png" is comparable
to that of  "ScanGear-Flatbed.png".   So setting  "Image Adjustment"  to
"None" in the "ScanGear" GUI  does produce a decent ADF scan  on the MB-
5150.   Now we "just" need to get the same result  from the "pixma"back-
end ...

By the way: On their web site at

   https://www.canon-europe.com/support/consumer_products/products/fax__multifunctionals/inkjet/maxify_mb_series/maxify_mb5150.html?type=drivers&language=en&os=linux%20(64-bit)

Canon is offering the source code for both, an IJ Printer Driver version
5.40 and ScanGear MP version 3.40, of which the former is even available
as Gentoo package "net-print/cnijfilter2"  version 5.90.  Would these be
of any help?

Sincerely,
  Rainer