[plug] OpenOffice.org in a pre-press environment.

[Craig Foster]

> -----Original Message-----
> From: plug-bounces at plug.linux.org.au 
> [mailto:plug-bounces at plug.linux.org.au] On Behalf Of Craig Ringer
> Sent: Sunday, 16 January 2005 4:28 PM
> To: Perth Linux User Group
> Subject: Re: [plug] OpenOffice.org in a pre-press environment.
> On Sun, 2005-01-16 at 11:50, James Devenish wrote:
<snip> 
> > In PDF terminology, I think these are "DeviceRGB" colours. The 
> > problems are twofold. Firstly, those DeviceRGB values can't 
> be used by 
> > a full- colour CMYK print process because such a process does not 
> > actually have any red, green or blue inks. Thus, the colour must be 
> > transformed from RGB to CMYK.
> 
> Typically this is done by the printer during preflight, where 
> necessary, with much wailing and gnashing of teeth. The RGB 
> colour space doesn't map perfectly onto the CMYK colour 
> space, and printers really prefer not to risk changing your 
> colour results. That said, any half-decent RIP (or preflight 
> tool) should be able to handle conversion from RGB "black" to 
> true greyscale black without any issues.
 
Agreed. Any man and his dog can put stuff to press. If they don't know how
to handle a simple job like this, I would doubt their skills.

> > Secondly, this produces a mirky and wasteful result because 
> the naive 
> > mathematical operation will give CMYK values of 1 1 1 0 (i.e. the 
> > printer will consume cyan, magenta and yellow inks at full 
> strength to 
> > produce a dark mirky brown instead of using the pure black ink).
> 
> The colour conversion process used in the RIP / preflight 
> tool usually applies "black pullout" to address this. Trouble 
> is, there's no exact right answer as to how much to leave as 
> mixed colour inks and how much should be applied in the black 
> channel instead.

GCR or "Black Pullout" is a tricky business and depends on whats being
printed, inks, dot pitch and other press stuff. A normal end user should
expect the printer to handle this. Designers on the other hand, will use
colour and black for effect such as "warm black" (Black with a bit of yellow
and magenta) but they'll most likely talked to the printer to get his
printers settings, or use ICC profiles. 

> > The general solution is to design a page in CMYK. 
> Alternatively, it is 
> > probably possible to go down the path of colour calibration 
> in which 
> > perceptual values are stored in the PDF and converted to 
> best- guess 
> > device values when the PDF in rendered on screen or in 
> print (this is 
> > what Mac OS X does).
> 
> If you embed ICC colour profiles in your PDF and make sure 
> all images are tagged with ICC profiles, it should be quite 
> safe to use an RGB PDF these days (so long as your printer 
> supports colour management and ideally PDF/X-3). Getting the 
> colour management right is usually harder than just 
> generating a proper CMYK PDF though.
> 
> > Better file a bug with the OOo team so that OOo will output in CMYK 
> > instead of RGB. This won't give you "WYSIWYG"
> > results, nor will it give your the result you'd get by paying a 
> > graphic designer, but it will make 'small office home office' 
> > production more accessible.
> 
> OO.o should /certainly/ output greyscales as real black 
> channel colours, whether targeting on-screen display or 
> print. CMYK conversion is harder because doing it 
> "automagically" is a little risky and can change the user's 
> colours. IMO it's best done at the printers, where they have 
> all the colour profiles for their press etc - but it seems 
> many printers don't have basic preflight tools for this sort 
> of thing (or just don't want to deal with it).

Generally, I'd tell people to find another printer. This is important stuff,
even an ex scanner salesperson & tech (like me) knows this stuff. If the
printer doesn't want to deal with this kind of stuff or buy the tools
required, I'd doubt his motivation for being in the printing and (pre)press
industry.

> In the end, I'm not sure OO.o is really the best app to be 
> using when generating PDF for print. The only free-software 
> app I'm familiar with that generates fairly good press-ready 
> PDF is Scribus. It may be worth looking into - 1.2.1 just 
> came out, and it's considerably improved.

<scratching chin> Interesting..... I'd always thought Linux lacked decent
CMYK tools, but that's could get people started...  
> --
> Craig Ringer

CraigF