[Scribus] grayscale images imported as RGB?

[Hal V. Engel]

On Tuesday 13 March 2007 14:37, Terence Chan wrote:
> Excuse my ignorance but why is it important/deirable to have greyscale
> images on the K plate only? I finished a book recently with lots
> of greyscale images colour profiled in RGB/CMYK PDF (set to "printer").
> The page proofs from the printer look just like what I wanted, so what's
> wrong with that?
>
> Terence
>
> On Tue, 13 Mar 2007, Vladimir Savic wrote:
> > Try! And prove you're wrong! Tested with Acrobar Pro from CS creative
> > suite. RGB input is not a bad solution at the first place. :) Output is
> > color profiled CMYK PDF. (which means that fallowing my procedure,
> > finally applied color profile will only effect visual appearance of K
> > plate, but not it's nature - it will be grayscale (that is K only), not
> > composite grayscale.)
> >
> > BTW, I'm running linux, so I don't have anything other then The GIMP to
> > work with. Using PS on win boxes is much faster/natural way to make CMYK
> > images without that much pain, but never tried it... :(
> >
> > Vlada
> >
> > > Setting the image to CMYK does work for me. I don't know wich app you
> > > use but if you convert
> > > your image to CMYK you should make sure you delete all data from the
> > > CMY channels and copy the original
> > > K or Grayscale data only to K or try "maximum Black" conversion mode
> > > (before you import them)
> > >
> > > Jon
> > >
> > > Am 12.03.2007 um 12:54 schrieb Vladimir Savic:
> > > > On Monday 12 March 2007 17:43:36 Terence Chan wrote:
> > > >> Yes, I believe this is normal behaviour for scribus - why is this
> > > >> a problem? So long as you apply the appropriate icc input and output
> > > >> profiles the greyscale images should appear ok when printed and on
> > > >> the screen.
> > > >>
> > > >> Terence
> > > >
> > > > Hmmm...
> > > > I was doing something obviously wrong here too (talking about
> > > > Scribus 1.3.3.x
> > > > not 1.3.4cvs). "Appropriate profile" is a key point. No profile can
> > > > ensure
> > > > grayscale RGB (picture in RGB color space but completely
> > > > constructed of r=g=b
> > > > values pixels) picture to appear on K plate only when PDF gets
> > > > token to
> > > > prepress office.
> > > > Right approach would be to ask of user if imported picture is
> > > > composite
> > > > grayscale picture or single color channel image. Fortunately, in
> > > > 1.3.4 there
> > > > is a simple solution: image effects -> apply colorize image and
> > > > give that
> > > > picture 'black' color colorization (Don't take further writing for
> > > > granted
> > > > but I think choosing 0%C 0%M 0%Y 100%K "in-Screibus hand made"
> > > > color doesn't
> > > > work correctly)
> > > >
> > > > Vlada
> > > >
> > > >> On Sun, 11 Mar 2007, Lila Pagola wrote:
> > > >>> hi!
> > > >>> I'm working with Scribus in a book, almost finished, because we
> > > >>> are in
> > > >>> press with everything except cover.
> > > >>>
> > > >>> Preparing the cover design for pre-press (I don't if in english
> > > >>> it's said
> > > >>> that way), I have found a rare behavoir of Scribus with grayscale
> > > >>> images:
> > > >>> they are considered as RGB files, in any format I try to import
> > > >>> them (PNG8, gif, tif). And If I import them as CMYK I have
> > > >>> information in the
> > > >>> 4 channels when the image is just black.
> > > >>>
> > > >>> Somebody has experiencied something similar? Am I doing something
> > > >>> wrong?
> > > >>> I did a quick search on the web and the list's archives and I
> > > >>> didn't find
> > > >>> any report of this problem.
> > > >>>
> > > >>> Our project has a wiki when we are uploading the problems and
> > > >>> solutions
> > > >>> we found, in spanish, sorry (and for my english sorry too)
> > > >>> the url is http://nomade.liminar.com.ar/wakka.php?wakka=MaBI
> > > >>>
> > > >>> Thanks in advance for any clue ...

In fact all that really matters is that in what ever color space is used (RGB, 
CMYK or some greyscale color space) that the resulting color is one that is 
neutral (gray) in that color space.  For example any color where R=G=B in 
sRGB or AdobeRGB would be neutral.  When this neutral image is sent to the 
physical printer it should be converted from what ever it's current color 
space is into the physical printers color space before being printed.  That 
conversion will result in the images being neutral when they are printed.  
This may not actually result in a grayscale image only using the K plate of 
the physical printer since the combination of paper and ink being used may 
actually result in a K plate only print having a color cast.  In other words 
it really does not matter what color space is used for gray in the document 
as long it is not ambiguous that the colors in question are shades of gray 
and as long as the document and the printing process are properly color 
managed. 
 
Hal