[GTALUG] colour management

[Russell Reiter]

On August 26, 2017 11:45:17 AM EDT, "Stewart C. Russell via talk" <
talk at gtalug.org> wrote:
>(subject changed from "Re: [GTALUG] Raspberry PI wifi problem")
>
>On 2017-08-25 03:49 PM, Russell via talk wrote:
>>
>> My biggest nice to have feature would be a comprehensive source of
>ICC lookup tables for linux.
>
>If you're meaning for scanners, generic manufacturer ones are kind of
>useless. Light sources age and shift, and so your generic calibration
>becomes less and less useful. If you have to have one of these files,
>dig about in the Windows or Mac driver package, as there's usually one
>there.

I just recently acquired Windows 10 with an hp mini I bought online. First
personally purchased MS Windows OS ever. I jumped from DOS 6.2 to Linux for
myself, leaving Windows to the business end of things. I learned M$ Windows
stuff on other peoples dime. I'm kind of frugal that way.

>
>With an ICC target — Wolf Faust sells cheap but good ones from
>http://www.targets.coloraid.de/ — it's easy to calibrate a scanner.
>I've
>always meant to
>
>a.) do a lightning talk on colour management;

I'd find that interesting. I've never colour calibrated a scanner, never
needed that kind of fine grained reproduction.

>
>b.) arrange a group buy of scanner targets. Wolf sells them *very*
>cheap
>if you're shipping more than one.
>
>I have a spare (stored in the dark, unused, technically expired but
>good
>enough) ITU target if anyone wants one. Wolf makes targets for the big
>repro companies, so his stuff is good. He's also been writing printer
>drivers since the early 1990s.
>
>You might also be surprised at what's living in /usr/share/color/icc
>already …
>
>> I wouldn't have to stop cups to be able to scan with my MFU.
>
>Is your AIO networked, or connected via USB? cups tends to hog the

USB, the problem for me, outside of the flimsy feed table which throws off
alerts about itself, is that I have to manually trigger a udev event to be
able to access the scanner.

If I reboot and have forgotten to stop cups service and then try to scan
with xsane, it cleans the print head and then the low colour tank indicator
on the unit flashes, even though the tank is full.

Simple Scan does nothing. If I just stop cups, and turn off and on the
power, simple scan works poorly but, xsane can't find the device at all. I
have to power it off by unplugging and then switch on again before xsane
recognizes something. However the scan quality is very much higher.

I think I have a couple of concurrent issues. One, there is something
mysteriously funky about connecting USB 2.0 B male downstream to 3.0
female. Not necessarily in the hardware, Linux afaik doesn't report ink
volume, MS will, so it looks like its more of a presentation layer issue.

Ink volume is a kind of colour property report. I think that xsane
start-scan command to the unit is being misinterpereted as clean head and
report ink volume when cups service is running.

The other thing is the modeswitching from printer to scanner, which I have
kluged.

At this point I could create a couple of system targets to stop cups before
xsane starts and start cups if lpq is populated but, since this is a photo
printer not in daily use, I keep the print daemon inactive. I scan much
more than I print.

There is a known issue with the infeed on Cannon Pixma. The fix is to
remove the flimsy plate and flex it by hand to reshape it so the feed works
consistantly. Rather than do that, I'll eventually replace it.

This one was a Christmas gift to print photos from the holidays. The
paperstops of the scan table are very precise and squared to the scan bed
for one button photocopying of pictures on the bed, so no futzing with
baseline registration when printing a scanned image.

>whole
>device over USB. xsane finds my networked Epson, but annoyingly all
>drivers (perhaps the hardware itself) can only scan at 8 bpp.

Well I would like a few more than 256 colours but in fact for my own day to
day use that would probably be fine. I'm not a real shutterbug and I dont
create a lot of personal/busines paper fallout at home.

>
> Stewart
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