Re: Canon Pro-100

On Tue, Dec 22, 2020 at 9:43 AM Ken Smolek <[email protected]> wrote:

Hello Ken,
Many thanks for your message, I am very impressed and delighted that you
have managed to get one of the Pro series working.
I am the current maintainer for the Canon backend, and would love to work
together to incorporate the code.

Then I came across a pristine Canon Pro-100 for almost nothing and
> bought it, which has turned out to be a monumental rabbit hole. But I'm
> retired and have nothing better to do, especially in a pandemic, so I
> tackled it.
>
> With no Gutenprint/CUPS driver, and little or no documentation (that
> mostly from Gutenprint and Ghostscript, nothing from Canon), it's been a
> very tedious process of reverse engineering of the command strings. And
> the Canon printer driver [print-canon.c:canon_setup_channels()] takes an
> approach to subchannels which doesn't work for the Pro-100, which, as
> near as I can tell, demands that channels be output in the order
> CMYcmkHL. In addition, the raster output string [formerly ESC(nn nn F
> data] has been expanded to take a 4-byte length, and is now ESC(N nn nn
> nn nn F data.
>
> To make a very long, 2-month story short, I have a working Canon Pro-100
> under Gutenprint which uses all 8 inks and prints photos which are not
> perfect, but are of pretty high quality. Images converted to grayscale
> in Gimp print very well, but I have been unable to get straight
> monochrome printing (using an inkset consisting of black, gray, and
> light gray - kHL) to work.
>
> I've tried very hard not to break existing code, but obviously there are
> no guarantees of that. Where I added significant code to handle the
> Pro-100, I generally did it by creating new functions, which are called
> only if the printer is PIXMA Pro100. In some cases, I simply added the
> Pro-100 to an already-existing set of printers in a long if statement.
> Code was added as necessary for inks, modes, media, etc. The mask
> protocol in print-canon.h is still a little mysterious to me, but I'm
> reluctant to mess with it more than necessary.
>
> [BTW, I started from a downloaded 5.3.3 tar file. I set up a local git
> repository with my changes in a Pro100 branch, so all modifications from
> the canonical version are visible.]
>
> Print quality improved dramatically when I included the standard Canon
> hue, sat and luminosity curves to the Pro-100 printer definition - that
> was when I realized I might have a really usable driver. But it's still
> not perfect - I've done some tweaking in the Adjust Output screen, but
> I'd love to be able to improve the curves and LUTs. Is there a
> description anywhere of how the hue/sat/lum arrays are generated?
>

Where did you get the "standard Canon" curves from?
I don't know how the existing ones are generated actually, there are 3 to
choose from.
Those for the iP4200 are apparently tuned to that printer, and may be
correct for some other printer models too.
Unless one actually has a printer to test, it is not really possible to
design matrices.
The Canon driver started out as a fork of the (now much more advanced)
Epson driver.

Robert, is there any background on the matrices in the Epson driver that
may help?

So, where do I go from here? This is very close to a driver I can use
> for my own prints, but it's not production software. And I have no way
> of regression testing to see what I may have broken. If you prefer, it
> can just stay here as a local modification for my personal use. Or we
> could attempt to integrate it in some way, possibly by creating a
> print-canon-pro.c which is completely separate from the existing
> print-canon.c. This would have been a reasonable way to go initially,
> but hindsight is 20-20, and I didn't
> really understand what I was getting myself into.
>

I would like to incorporate the code if possible. I have some understanding
of the Canon driver code, since I have been touching it for some years, but
I do not have a very clear understanding of ink handling and low-level
routines even now unfortunately.
Most of my work has been trying to add commands, and various options for
the commands.
A major work in progress is to get CD printing to work systematically, so
if you have time on your hands, I would love some help with that.

Another possibility is to implement an IPP driver for the printer and
> try to eliminate the Pro100 ppd entirely. That's an attractive
> possibility to me, but I'm still vague on the actual process, and I'll
> have to take another look at the IPP sample code to see just how
> complicated it will be. Your opinions are welcome.
>

Robert, do you have any opinions on this?

Best regards,
Gernot Hassenpflug

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