Forum: Inkscape 0.48 alpha report

Downloaded the 0.48 alpha package and started to play with it.
My first interest was the capability to use CMYK colors. Before 0.48
the doctrine was that you  could use three out of four CMYK  colors
but not 4 out of 4. With 0.48 as you move one CMYK slider one of
the others tends to jump back to zero but not always. By fiddling
some I was able to establish rich black at 60,40,40,100.  Given
that internally Inkscape is still using the RGB color model I wonder
if this is a color that will actually be used for output.  There are
several swatch bars available but none seem to be expressed in
CMYK terms. If in fact all possible CMYK colors can be expressed in
RGB terms then it should be possible  to use pseudo CMYK colors
on the  Inkscape color bar and pass these shades on to e.g.,
Scribus in RGB format. I would be interested in comments from the
developers on this.
--
John Culleton
Wexford Press
"Create Book Covers with Scribus"
Printable E-book 38 pages $5.95
http://www.scribd.com/doc/24676863/
http://www.booklocker.com/books/4055.html

On Jun 11, 2010, at 5:09 PM, John Culleton wrote:

>  Given 
> that internally Inkscape is still using the RGB color model I wonder 
> if this is a color that will actually be used for output.

It does... but doesn't quite have to.

If you set a true CMYK color, then it stays as 4 values.

> There are 
> several swatch bars available but none seem to be expressed in 
> CMYK terms.

"CMYK" in and of itself is meaningless as far as defining color goes. 
"RGB" is also fairly meaningless, but the good news is that SVG 
specifies that it does all base colors in "sRGB", and not just random 
"RGB".

To get control of color, you need to specify an ICC color profile that 
states exactly what visual result the random numeric input results in. 
There are a few 'standard' CMYK profiles that are similar to the 
'standard' "sRGB" color profile.

So... just reference one (or more) ICC color profiles in your SVG 
document and then the "CMS" picker (and to some degree the others) will 
let you specify colors in *true* CMYK values... and ones that Scibus can 
even import.


> If in fact all possible CMYK colors can be expressed in 
> RGB terms then it should be possible  to use pseudo CMYK colors 
> on the  Inkscape color bar and pass these shades on to e.g., 
> Scribus in RGB format. I would be interested in comments from the 
> developers on this.

No, it's not possible to express all CMYK colors in RGB terms, at least 
not with the numeric limits used in SVG.

if you're interested in more details, you can get the slides and watch a 
video of my presentation on this at linux.conf.au 2009.
http://codewideopen.blogspot.com/2009/02/color-talk-at-linuxconfau.html

On Saturday 12 June 2010 02:31:01 Jon Cruz wrote:
> On Jun 11, 2010, at 5:09 PM, John Culleton wrote:
> >  Given
> > that internally Inkscape is still using the RGB color model I 
wonder
> > if this is a color that will actually be used for output.
>
> It does... but doesn't quite have to.
>
> If you set a true CMYK color, then it stays as 4 values.
>
> > There are
> > several swatch bars available but none seem to be expressed 
in
> > CMYK terms.
>
> "CMYK" in and of itself is meaningless as far as defining color 
goes. "RGB"
> is also fairly meaningless, but the good news is that SVG 
specifies that it
> does all base colors in "sRGB", and not just random "RGB".
>
> To get control of color, you need to specify an ICC color profile 
that
> states exactly what visual result the random numeric input 
results in.
> There are a few 'standard' CMYK profiles that are similar to the 
'standard'
> "sRGB" color profile.
>
> So... just reference one (or more) ICC color profiles in your SVG 
document
> and then the "CMS" picker (and to some degree the others) will 
let you
> specify colors in *true* CMYK values... and ones that Scibus can 
even
> import.
>
> > If in fact all possible CMYK colors can be expressed in
> > RGB terms then it should be possible  to use pseudo CMYK 
colors
> > on the  Inkscape color bar and pass these shades on to e.g.,
> > Scribus in RGB format. I would be interested in comments 
from the
> > developers on this.
>
> No, it's not possible to express all CMYK colors in RGB terms, at 
least not
> with the numeric limits used in SVG.
>
> if you're interested in more details, you can get the slides and 
watch a
> video of my presentation on this at linux.conf.au 2009.
> http://codewideopen.blogspot.com/2009/02/color-talk-at-
linuxconfau.html
>
>
I viewed the video and now I know more about what I don't know.
If I install an ICC profile, say of the SWOP family, and I try to use
colors in the CMYK gamut, is there a way to save the file to e.g.,
pdf with the colors expressed in CMYK terms? Or must Inkscape
always save files in RGB color model? I know that I can import the
file into Scribus and save that in CMYK color model but I am
looking for a solution that does not involve another major
program.

--
John Culleton
Wexford Press
"Create Book Covers with Scribus"
Printable E-book 38 pages $5.95
http://www.scribd.com/doc/24676863/
http://www.booklocker.com/books/4055.html

On Jun 12, 2010, at 12:05 PM, John Culleton wrote:

> I viewed the video and now I know more about what I don't know.
> If I install an ICC profile, say of the SWOP family, and I try to use 
> colors in the CMYK gamut, is there a way to save the file to e.g., 
> pdf with the colors expressed in CMYK terms? Or must Inkscape 
> always save files in RGB color model? I know that I can import the 
> file into Scribus and save that in CMYK color model but I am 
> looking for a solution that does not involve another major 
> program.

if you link a CMYK profile like SWOP or fogra, then edit colors using 
the "CMS" picker, then Inkscape saves the colors in *both* the specific 
CMYK model *and* the sRGB model as a fallback:

#2f8d33 icc-color(Fogra27L-CMYK-Coated-Press, 0.75777829, 0.00038148, 
0.99993896, 0.24254215)


We're working with the Cairo people to try to get a proper API figured 
out to support CMYK+spot ending up in a PDF. In the mean time Scribus 
has been a default "go to" program since it is a top end publishing tool 
focused on creating print-house ready PDF output for some time now.