Re: [Gimp-print-devel] Wow!

[<sh...@al...>]

>    I don't have a lot of experience here, but I've read up on the
>    publicly available documentation on the web and I have the CIElab
>    coordinate measurements of the inks used in the ESP750.  I don't
>    know if these are used in the current print plugin or not.
> 
> They're not, but that would be useful information.  Currently there's
> some weird ratio stuff going on.  That would best be replaced by
> actual data.

I won't mention how I got this information since it's not available in
Epson level 1 programming documents.  I normally like to give credit where
credit is due, but, in this case, it may be better not to.

Here are the numbers:

    (for 720 DPI on plain paper)

    Color             L       A       B
    -------------  ------  ------  ------
    White           90.71    1.12   -4.37
    Cyan            52.40  -26.85  -39.29
    Magenta         55.56   61.60   -3.79
    Yellow          84.35    2.77   68.90
    Black           27.67    1.30   -0.76
    Light Cyan      67.69  -28.57  -31.96
    Light Magenta   66.63   46.71  -11.90

(Note to Epson Corporate types trolling the net:  The message I wrote
earlier listing the people I had contacted on this topic was *not* a
complete list. (Ok, this DVD case is making me a little paranoid...))

It remains to be seen whether the "correct" color transforms will actually
improve results over more trial and error methods.  Reading the documents
on color transforms, it seems that there is still a lot of trial and
error involved in color science.

> The other thing that's wrong is that those ratios are hardcoded, so
> printers with different inks won't do the right thing.  The right
> thing is for there to be an initialization/free routine for each
> dithering routine that is called by the printer driver.

That doesn't sound hard to fix.

> Interested in this stuff?

Yes.  I'll take a crack at it later this evening.


Do you have any guidelines for CVS commissions?  I gather that since I'm now
a registered developer, I have commission privileges, but some project
leaders I know prefer to approve each patch individually before commission.

Eric