Sorry that it took so long, Simon ;)

Anyways, I had some conversation with two graphics designers about CMYK
problems and the Gimp at the Systems, and I think it might be worthwhile
to read the following "sometimes true" observations. Remember, they are
hearsay ;)

   1. "colour matching for photos is a don't care". Ok, this is a blatant
      lie, however, exact colours are not that much of a concern for
      photos. Much more important are logo colours (most companies have
      pretty strict definitions of these). If a photo doesn't exactly
      match the screen colours ("which screen colours, anyways") this
      is often not a reason to not use gimp. If a logo colour can't be
      reproduced, however, it keeps Gimp from being used.

   2. "Logo colours are not CMYK". Yupp. Logo "colours" might not be
      representable in CMYK at all (gold etc...). Even if, you often (but
      not always) want seperate planes for important colours.

      Most uses of spot colours want the concept of an "indexed channel",
      i.e. a channel where each value represents a different palette
      colour. No bleeding with image contents.

      Gimp's channels can be used instead, which is not that perfect for
      all uses, but exists and at least photoshop doesn't offer a better
      solution ;) They also allow gradients of a single spot colour, which
      indexed channels wouldn't allow. Wether all this makes them easier
      or harder to use is something to explore.

   3. "You don't print from within the gimp". At least you don't print
      brochures from within the Gimp. You use gimp for artwork, often the
      logos, but you obviously don't set text using the Gimp. You instead
      import images into some layout program (quark xpress ;).

      I was told that the principal reason for bad quality of gimp
      images within quarkxpress is that quarkxpress imports gimp's rgb
      tiffs like garbage. I was told that loading the rgb data into
      photoshop, associating sRGB with it (changing _nothing_ else)
      improved the quality very much, making the results reproducable on
      printers. Without absolute colours, they look different.

   4. "Cheap CMYK vs. RGB makes a difference". Many programs also seem
      to have problems ("looks like shit") with RGB data, not because it
      isn't associated with a colourspace, but because it's RGB. Cheaply
      ("formula") converted CMYK data seems to help a lot here. That
      CMY has an additional K is of no concern - users don't sue this
      additional level of freedom,

      Things like trapping are handled by other programs or by very
      expensive photoshop plug-ins.

   5. "Logos are done by overlays". At least one method of using spot
      colours is to create them as seperate channels. Tiff/Eps are
      reportadly able to save additional channels in a way that a program
      can read them sensibly.

      The spot colour "planes" are then laid over the other graphics. For
      this to work a mask is necessary, since channels range from white
      (not transparent) to "channel colour", at leats in quarkxpress.

      It seems that traditional masks are not what's called for - instead
      you want a path saved in the tiff/eps file (don't ask me wether that
      is possible). This clipping path is then used for the overlay - gimp
      can't create this kind of paths, nor can it save it.


   If one were so bold as to draw some conclusions, they would probably be very
   similar to these:

   1. Enhance the tiff/eps save plug-ins to do cheap RGB->CMYK conversion. This
      would work around conversion problems in other programs.

   2. Associate sRGB or any other colourspace with the saved data in
      tiff/eps.  It doesn't matter wether it's true or not, just give
      programs something to depend on.

   3. Educate users about channels and what they can be used for - on this
      Systems I was frequently confronted with users who were unhappy with
      the gimp because it didn't allow them to do things as easily as under
      photoshop. Often(!) I was able to get exactly the same results, with
      a much easier and faster sequence than the one that user used with

   This could be a start, to work around bugs in other programs. Also
   relatively cheap, unlike the following:

   4. Find out wether saving paths as paths as opposed to masks is really
      required to do overlays in common layout programs. If yes:

   4a. enhance the path tool to be able to work with generic paths (holes,
       multipart etc.).

   4b. enhance the tiff/eps plug-ins to be able to save these paths together
       with channels.

   4b. (optional) make tiff/eps save images together with their channels in
       the same file.

   5. Implement "indexed channels", or somethign else that makes handling spot
      colours easier. An easy way is to use one channel for each spot colour.

   I certainly forgot something, probably because I should have written this
   much earlier (afetr the systems), but if I had that much time... *sigh* ;)

      -----==-                                             |
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      ---==---(_)__  __ ____  __       Marc Lehmann      +--
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    The choice of a GNU generation                       |
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