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GIMP 2.4 Released 596

Enselic writes "After almost three years since the release of GIMP 2.2, the GIMP developers have just announced the release of GIMP 2.4. The release notes speak of scalable bitmap brushes, redesigned rectangle/ellipse selection tools, redesigned crop tool, a new foreground selection tool, a new align tool, reorganized menu layouts, improved zoomed in/zoomed out image display quality, improved printing and color management support and a new perspective clone tool."
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GIMP 2.4 Released

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  • GIMP 2.3? (Score:3, Insightful)

    by bvimo ( 780026 ) on Wednesday October 24, 2007 @07:11PM (#21106661)
    How long since GIMP 2.3 was released or am I missing something important?
    • Re:GIMP 2.3? (Score:4, Informative)

      by ScislaC ( 827506 ) on Wednesday October 24, 2007 @07:13PM (#21106681)
      2.3 was the devel branch leading up to 2.4
    • Re:GIMP 2.3? (Score:4, Informative)

      by moderatorrater ( 1095745 ) on Wednesday October 24, 2007 @07:16PM (#21106711)
      I'm guessing they have the unix version numbering, where even numbers are release, odd numbers are development.
      • Re: (Score:3, Informative)

        by Anonymous Coward
        I think the word you are looking for is 'linux'. The even/odd numbering convention is not used by any of the *BSDs, or by Solaris, or by plenty of unix targetted software projects.
    • Re:GIMP 2.3? (Score:5, Informative)

      by Raphael ( 18701 ) on Wednesday October 24, 2007 @07:22PM (#21106805) Homepage Journal

      The stable GIMP releases have even numbers. The last stable release before 2.4.x was GIMP 2.2.x, starting with 2.2.0 released in December 2004. So that was almost three years ago. There were several bug-fix releases in the meantime, up to 2.2.17.

      The unstable 2.3.x releases ended with the last versions becoming release candidates for 2.4.

      • Not everywhere, but in enough places that I'd think people would notice.

        For example: The Linux kernel. I'm running 2.6.22. The 2 is most likely incrementing normally, since there was a 1.0.0 release, that was considered "stable", or as much as it can be. The 22 also increments normally, I think -- though I may be wrong about that.

        But I did upgrade directly from 2.4 to 2.6. This is because Linux 2.5 was a development branch. Highly unstable, but it went on for quite awhile, with the most essential parts back
  • What about... (Score:5, Interesting)

    by calebt3 ( 1098475 ) on Wednesday October 24, 2007 @07:13PM (#21106675)
    CMYK colors and other functionality that keeps it from being able to replace Photoshop completely? Not to understate all the effort that has been put into it, but something like that does seem pretty basic for three years of development.
    • patents (Score:5, Interesting)

      by Anonymous Coward on Wednesday October 24, 2007 @07:36PM (#21106973)
      A lot of the key algorithms, particularly for color space conversion, are patented. Guess who holds a bunch of those patents?
      • Re:patents (Score:5, Insightful)

        by Anpheus ( 908711 ) on Wednesday October 24, 2007 @07:44PM (#21107083)
        And they can't release a non-US version that people in the US will "accidentally" download?
        • Re:patents (Score:4, Insightful)

          by westlake ( 615356 ) on Wednesday October 24, 2007 @09:46PM (#21108283)
          And they can't release a non-US version that people in the US will "accidentally" download?

          in our metro newspaper there is not one job opening in photography that does not include expertise in Photoshop as a requirement.

          these shops have no interest in a program that increases their legal exposure. no interest in a program that can't deliver basic functionality and live within the law.

          • Re: (Score:3, Informative)

            by sgtron ( 35704 )
            The paper I shoot for doesn't require squat. Just shoot pictures. If they're good, they use them. We have editors that use Photoshop to crop, resize and color correct if necessary. But. If they wanted to use the gimp they could do that too. No one holds a gun to their head and says use Photoshop. It's just the "industry standard", but if you can do the job with different tools then go for it.
          • Re:patents (Score:4, Interesting)

            by theshowmecanuck ( 703852 ) on Wednesday October 24, 2007 @10:59PM (#21108859) Journal
            World population: 6.6 billion
            U.S. population: 0.3 billion
      • Re:patents (Score:5, Informative)

        by NMerriam ( 15122 ) <> on Wednesday October 24, 2007 @09:52PM (#21108333) Homepage

        A lot of the key algorithms, particularly for color space conversion, are patented. Guess who holds a bunch of those patents?

        Oh please. That is not and never has been the problem. The problem is that the program was initially created with the assumption that all images would be 8-bit RGB, and then a huge amount of code was built on top of that silly assumption.

        Yes, you can run into IP issues with things like Pantone, DIC, Toyo, or a particular set of CMYK transforms, etc, but that has nothing to do with the limitations of the GIMP. There are plenty of other image editors that have no problem doing color space conversions or dealing with >8-bit images because they were written by programmers who actually listen to graphics professionals.
      • Re: (Score:3, Insightful)

        by terrymr ( 316118 )
        There's patents for RGB->CMY(K) conversion ?

        Crap I must have violated those a bunch of times when I bought my first color printer and had to write software to drive it ... this was probably nearly 20 years ago. You'd think that if there were such a patent it would have expired long ago given that computer driven CMYK printing has been around for a long time relatively speaking.
    • SIOX ! (Score:3, Informative)

      by DrYak ( 748999 )
      On the other hand, Gimp 2.4 has SIOX [] builtin [], the single best tool for manipulating photographs.

      (For those who don't know : you make a coarse free-hand circle around your object, then you scribble on the object, and SIOX takes care to extract the object from the surrounding).
    • Re: (Score:3, Interesting)

      by gringer ( 252588 )
      Last time I checked (about 10 seconds ago, on a Debian unstable box, v2.4.0-rc3), it seemed like GIMP could do a few colour related things, such as:
      • Assigning a colour profile (*.icc, *.icm)
      • Converting to a colour profile (with interesting sounding words and phrases like "rendering intent, perceptual, relative colorimetric, black point compensation")
      • Decomposing an image into separate colourspace components (like RGB, CMY, CMYK, LAB, YCbCr ITU R470)
      • Recomposing an image that was previously decomposed (using the
    • there is a CYMK plugin for the gimp called separate+ @ []

      it is, as many solo projects, has always been in beta, but it worked well for me (though I am not really a graphic artist).

      And as screwed up as the whole patent system is, you still can't patent something like CYMK because it is something fundamental to nature. What would be patentable would be the process. Two things can have the same end result as long as they don't use the same method, unles
  • by moderatorrater ( 1095745 ) on Wednesday October 24, 2007 @07:14PM (#21106683)
    I hope they moved the gui closer to that of Paintshop. I can't tell you how many times I've been unable to edit an image for one reason or another, or the expected behavior is what happens. I know a lot of people love GIMP and its scripting abilities, but seriously, when they're trying to enter the market dominated by a few programs with that same gui and behavior, they should replicate it.
    • by jklappenbach ( 824031 ) on Wednesday October 24, 2007 @07:21PM (#21106783) Journal
      I don't know about Paintshop, but there's a Photoshop-esque makeover for GIMP called Gimpshop. It has a couple of rough edges, but it's a testament to the modularity of design that a self-declared novice developer could take the existing GIMP framework and remake it in PS's image.

      The download link can be found here. []
    • by domatic ( 1128127 ) on Wednesday October 24, 2007 @07:26PM (#21106837)

      but seriously, when they're trying to enter the market dominated by a few programs with that same gui and behavior, they should replicate it.

      But then there is this other group of people who will complain that GIMP is just being a PhotoShop wannabe and not innovating. If one wants something that acts Just Like PhotoShop then the thing to do is suck it up and buy PhotoShop.
      • by Blakey Rat ( 99501 ) on Wednesday October 24, 2007 @07:28PM (#21106877)
        But then there is this other group of people who will complain that GIMP is just being a PhotoShop wannabe and not innovating.

        Yeah, but it's already not innovating. It's just not innovating with a crappy UI, as opposed to not innovating with a good UI.

        BTW, a good UI doesn't (necessarily) mean Photoshop. Paint.NET for Windows has a pretty damned good UI, and it's not much like Photoshop at all.
        • Re: (Score:3, Interesting)

          Gimp's UI makes more sense on a XWindows system where you can set the individual sections of the UI to stay on top. For instance, I can keep the image full-screen on one monitor while using the editing tools on a second monitor. I'd like to see a single-window app like Photoshop do that!
          • by ArAgost ( 853804 ) on Wednesday October 24, 2007 @07:44PM (#21107091) Homepage
            Photoshop does this pretty well on my Mac :)
          • by MobileTatsu-NJG ( 946591 ) on Wednesday October 24, 2007 @08:15PM (#21107403)
            "For instance, I can keep the image full-screen on one monitor while using the editing tools on a second monitor. I'd like to see a single-window app like Photoshop do that!"

            Despite popular belief, Photoshop's panels aren't stuck inside of the parent window. You can do exactly as you described in Photoshop, and it's been that way for at least two years.

          • by moosesocks ( 264553 ) on Wednesday October 24, 2007 @08:28PM (#21107537) Homepage
            The single-window paradigm is a limitation of Windows, and not necessarily Photoshop. The mac version handles multiple monitors gracefully, and always has. The tool palettes also disappear when the app's not in focus -- there's no reason why they need to be separate windows, or even visible when the app's not being used.

            Photoshop is also one of the few apps where the "Menus at the top" scheme makes sense virtually all the time. There are cases in which I don't like it, but for applications like Photoshop or the GIMP, which commonly manage several windows at once, there is absolutely no doubt that Apple's windowing paradigm is the best of the bunch. It certainly accounts for a good portion of Apple's dominance in the creative design industry dating back to the 90s.

            I believe that recent versions of PS gained the ability to pop the canvas and pallets out of the main "root" window on Windows. You've still got the root window hanging out somewhere with the menubar in it, but you don't actually need to have anything in it. It's not optimal, but it's a limitation of the OS more than anything else.

            (Disclaimer: I'm not suggesting Apple's got the best scheme overall. There are certainly situations where Windows or X are clearly more efficient, and there are a lot of aspects of the OS X GUI that "bug" me. My "ideal" GUI would probably be some combination of Windows 2000, Mac OSX, and Xfce)
        • by GiMP ( 10923 ) on Wednesday October 24, 2007 @07:37PM (#21106983)
          What exactly is wrong with the UI in the Gimp? I have always preferred the UI of the Gimp to Photoshop. I think the biggest complaint of users of Paintshop and Photoshop is that the Gimp does not use MDI. Yet, for many, this is an advantage as it works better with multiple monitors and allows for greater multitasking. (Linux and MacOS users tend not to maximize apps). Plus, if you really want MDI, just use a virtual desktop. Even Vista has them, and they offload the "window grouping" from the application to the OS, like it should be done.
          • by Blakey Rat ( 99501 ) on Wednesday October 24, 2007 @07:58PM (#21107239)
            Dude, your username is "GiMP". Would you seriously ever admit any shortcoming to a product so beloved you named your user account after it? Seriously.
          • Re: (Score:3, Interesting)

            by fyngyrz ( 762201 ) *

            Actually, my biggest complaint about the Gimp (v2.2 on the Mac), and the biggest single time-waster, is that it doesn't remember many user settings. For example, I open the program, go to open an image, it's forgotten - again - where I was (in my image directory, where else?) when I closed the program. Time to navigate the filesystem tree... again... I go to scale an image, and it's forgotten I want bicubic, that I want percent, not pixels - and this is inside the very same session. A whole bunch of UI int

          • by Mr Z ( 6791 ) on Wednesday October 24, 2007 @08:21PM (#21107465) Homepage Journal

            I can tell you some things that drive me nuts in GIMP 2.2. (I haven't tried 2.4 yet.)

            • Pet Peeve #1: Image selection in the layers dialog

              The Layers dialog has two modes for deciding which image's layers it'll tell you about: Either you have to explicitly select it from a drop-down, or have it auto-switch to the last image which had focus. Either way, more often than not, it seems to have the wrong image selected for me. Why?

              If I'm hopping back and forth between images, say, cutting things from one and pasting them in the other, the drop-down selection will be wrong almost 100% of the time, simply because I'm hopping back and forth between images. So even though I've raised the imagine I'm interested in, and perhaps pasted something into it (which I now need to go anchor to a layer), the layers dialog points at the image I cut from, not the image I'm pasting into. So what about automatic mode?

              That one sucks too. I have my window manager set to "focus follows mouse." I have only so much screen real estate. In all likelihood, the image I cut from or yet some other image lies on the path between the image I pasted in, and the layers dialog. In some cases, it can be next to impossible to move from the image I'm working with and the layers dialog without brushing past another image--thereby causing the layers dialog to select the wrong image. Again, it loses.

              What I really want is the layers dialog to pick up the image I most recently interacted with. Gaining focus does not count as interaction. I should have to click something (even dead-air) or press a key to send an event into a given image's window before the layers dialog switches over to that image.

            • Pet peeve #2: Layer naming in the layers dialog

              If you want to rename a layer in Gimp, you can double click its name in the layers dialog and start typing. So far, so good. BUT, if you don't hit [Enter], but instead just move along and click elsewhere, it'll revert your edit. This makes editing a large number of names really tedious and error prone.

              (I've got a few other pet peeves with the layers dialog, such as lacking a way to select a layer AND make it the only visible layer in one go, or locking subgroups of layers together for motion rather than only having a global "lock together", or selecting groups of layers to act on simultaneously with a filter, or raising/lowering layers as a group, but I'll stop there.)

            • Pet peeve #3: Editing at image boundaries.

              If your image is smaller than the image window, you can over-stroke an image, which is great. You can even do point-to-point strokes with both endpoints outside the image. This is fairly handy. You can't do this, though, if the image is greater than or equal to the visible area. There's no overstroke zone around the image. You either have to zoom out, or make an oversized canvas to center your image in.

              Ok, suppose I go the oversized canvas route... oversized by how much? It really depends on how zoomed in or out you are. In reality, the amount of overstroke zone you need remains fairly fixed regardless of zoom level, so this isn't really an ideal solution.

            • Pet Peeve #4: Getting the wrong layer when trying to move things

              If a given layer has a lot of "thin" structures in a sea of transparency, the move tool often grabs the layer behind rather than the layer intended, even if the intended layer is the currently active layer. GIMP should "fuzz" the opaque areas out a little bit to make them more grabbable, because chances are that's what the user wishes to move. I don't remember a time when I accidentally grabbed a layer that was too high on the Z-ordering. I curse endlessly when I grab the layer below the one I wanted though, and that happens regularly.

            • Pet Peeve #5: Not actually selecting the tool I just clicked.

              If I click on a tool and move away too quickly, the tool gets a highlight box around it, but doesn't actually get se

            • by fyngyrz ( 762201 ) * on Wednesday October 24, 2007 @08:48PM (#21107763) Homepage Journal

              Interesting. Have you tried WinImages (if you're working under Windows)? It addresses all those issues, and many more. The UI is not like Photoshop's or the Gimp's, and is demonstrably more efficient in terms of what gets done per UI interaction count.

              Sounds like you're a real layers fan; WinImages has more layering power than anything else out there, hands down. 70+ blend modes, non-destructive geometric edits including scaling and rotation and a lot more.

              I know this because I wrote a lot of it. ;-)

    • by Hennell ( 1005107 ) on Wednesday October 24, 2007 @07:41PM (#21107035) Homepage
      If you have actual ideas for the GIMP UI go mention them at [] rather then just complaining here. They are aware the UI is generally disliked, they just need the best ideas of how to change it.
      Did the Ancient Egyptians play stone, papyrus, scimitar?
      • Re: (Score:3, Insightful)

        That's actually not useful in the slightest, because they're not interested in becoming more like Photoshop, they require a reason for changing the UI. Apparently they don't realize, completely ignore or have too much of a chip on their shoulder to admit that sometimes "because everyone on the fucking earth already knows how to do it this way" isn't a valid reason.
    • by blhack ( 921171 ) * on Wednesday October 24, 2007 @07:44PM (#21107087)

      Photoshop is going to soon suffer the same problem that i see for IBM. Open source is really starting to gain momentum. My fellow art nerds and I are all poor. We can't afford to go out and buy expensive software like photoshop; so what do we do? We go out and buy a wacom, get ourselves a copy of the GIMP and go to work. When we start getting ourselves into decision making positions, what are we going to choose? A very expensive and (imho) difficult to use piece of software like photoshop? Or a very familiar, and 100% free piece of software like the gimp?

      Similarly, IBM has really shot themselves in the foot with the OS/400 platform. Here you have a a really really rock solid piece of software, arguably one of the most stable operating system/platforms in existence today, but you have a problem. If I wanted to go out and learn OS/400, I mean REALLY learn it (the way that i can with Linux/BSD) I wouldn't be able to. It is FARRRR to expensive for a hobbyist like myselft to get into.
      Now ask yourself, if I, or my equally poor nerd brethren, go out into the job market and are tasked with building a database for whoever we start working for, what are we going to choose? Are we going to go with the familiar, very capable, and very FREE database called MySQL or Postgres (running on top of a *nix of course)? Or are we going to opt for a very cumbersum (I mean this from the perspective of somebody who has never developed on it before, it might be very elegant for all i know) very expensive, and VERY unfamiliar database such as DB2 (which is what runs on OS/400).

      Both IBM and adobe have shot themselves in the foot in this regard. Today's hobbyists are tomorrows decision makers, and they are going to choose what they are accustomed to.
      • by asuffield ( 111848 ) <> on Thursday October 25, 2007 @05:06AM (#21110739)

        Similarly, IBM has really shot themselves in the foot with the OS/400 platform. Here you have a a really really rock solid piece of software, arguably one of the most stable operating system/platforms in existence today, but you have a problem. If I wanted to go out and learn OS/400, I mean REALLY learn it (the way that i can with Linux/BSD) I wouldn't be able to. It is FARRRR to expensive for a hobbyist like myselft to get into.

        They don't care. If your budget doesn't have a minimum of six zeros on the end of it, IBM is entirely disinterested in your existence.

        IBM big iron is designed for those people who cannot use anything else. They have no competition. It doesn't matter if you prefer mysql or whatever - it cannot handle those kinds of loads, because it can't scale up to clusters of hundreds of thousands of CPUs. You, as a person who uses things like mysql, probably have no conception that those kinds of loads even exist. There are probably only a few hundred users in the world who need it. Nonetheless, their problems are real and have to be solved. IBM mainframe hardware is the only way to do it, so they pay a premium measured in millions. We are talking about problems that cannot be solved without filling an entire BUILDING with hardware. Most of them are related to the financial industry, who have to be able to process all the transactions in the world in real time, and where any failure of the system would cause irreparable damage to the world economy. This is up in the space where a system failure really could throw large countries into a recession overnight, so it absolutely has to be missile-proof.

        This is not a consumer industry. Hobbyists are irrelevant. The consumer industry will always continue to grow and occupy most of the world, but it is never going to be able to supply those few hundred at the top, and there is always going to be a need for IBM (or somebody very similar to them) to service their needs. And there's nothing wrong with that.
  • by Fry-kun ( 619632 ) on Wednesday October 24, 2007 @07:19PM (#21106749)
    I've recommended some artists to try gimp instead of proprietary stuff. The major complaints were about drawing tablet support. Gimp has tablet support, but the options available to the artist are very limited. Also, there are no smoothing algorithms for tablet-drawn strokes - a pretty major drawback if you draw on the computer instead of scanning things in.
    Other than that, gimp is awesome - and almost everything you can think of is available as a plugin - I've already tried the new context-sensitive resizing plugin (context-sensitive resizing has been mentioned a few months ago on /.)
    • by pbhj ( 607776 ) on Wednesday October 24, 2007 @07:38PM (#21107001) Homepage Journal
      Have you tried inkscape for tablet support? This appears to come from GTK so YMMV but is stated to support pressure and angle sensitivity.

      I haven't, but I love the app. They've made considerable advances in the last couple of releases. I know there's a tutorial by a guy who draws and shades comics using it. Also that you can simplify lines or using some (built in python) scripts add jitter or add jitter as you draw.

      If you've not tried it recently it's worth a punt.

      I'm using Slackware 12 and installed the development release via autopackage (
  • by szyzyg ( 7313 ) on Wednesday October 24, 2007 @07:19PM (#21106753)
    I do hope they've added support for colour depths greater than 8 bits....
    • Re: (Score:3, Informative)

      by szyzyg ( 7313 )
      WEll now it loads by 48bpp images without warning me that it's converting them to 24bpp images... and it converts them anyway. so a step back if anything in this department.
  • by domatic ( 1128127 ) on Wednesday October 24, 2007 @07:23PM (#21106815)
    Maybe 5 of the posts will have something actually illuminating. The rest of them will be GIMP and Photoshop fanbois going at each other. Let me save everybody the trouble.

    GIMP has an unprofessional name! Waaaaaaaaaaah!
    GIMP only does 8-bit color! Waaaaaaaaaaah!
    GIMP isn't UI identical to PhotoShop on every menu 3 levels deep! Waaaaaaaaaaaah!
    GIMP manages windows sucky! Waaaaaaaaaaaaaaah!

    Does not! Does too! Does not!.................
  • by je ne sais quoi ( 987177 ) on Wednesday October 24, 2007 @07:31PM (#21106907)
    I've been using this in the debian unstable repo for a few weeks now and I've found the redesigns are both intuitive and useful. I especially like the new selection tool, it's much easier to select an area and then change the selection after you realized you didn't hit the right pixel. Kudos to the GIMP team!!

    P.S. Although the GTK2 (i.e. GIMP Tool Kit) file picker is still slow as molasses in directories with large numbers of files. I had to hack firefox to get it to use it's native file picker once again because I got tired of waiting 30 seconds or more each time I wanted to save a file.
  • Fake! (Score:4, Funny)

    by DigitAl56K ( 805623 ) on Wednesday October 24, 2007 @07:54PM (#21107197)
    The linked site looks 'shopped.
  • by Erikderzweite ( 1146485 ) on Wednesday October 24, 2007 @08:08PM (#21107331)
    GIMP was NEVER intended to replace, duplicate or mimic photoshop. Neither was it created to draw users from photoshop. Unfamiliar doesn't mean bad or uncomfortable. They go their own way. Some like it, some don't. You are free to use gimpshop if you like to. I really see no points in this interface discussion.
  • by samwichse ( 1056268 ) on Wednesday October 24, 2007 @09:07PM (#21107937)
    Probably the most useful thing in this new release is the barrel distortion correction abilities and red eye tools. I haven't gotten to play with it yet, but I hope it enables setting/saving lens parameters for different cameras.

    This will definitely streamline my photo editing, as I had to go to panotools and hugin to correct the barrel distortion in my point-and-shoot cameras, but the gimp for color correction, cropping, etc. The improved color menu layout and cropping tools will be great (I always hated that alternate-diagonals cropping system it had before).

    The 16 bit color and CMYK, I couldn't give half a crap about. I mean, what proportion of gimp users need that stuff anyway? One percent? Half a percent? I think most gimp detractors just like panning something for the sake of it.

    A GIMP user for years.
  • by Teilo ( 91279 ) on Wednesday October 24, 2007 @09:57PM (#21108367) Homepage
    The digital color world is slowly but steadily shifting to an RGB workflow. The one thing that has impeded this move is the use of 8-bit color, which effectively means mapping a 32-bit color space to a 24-bit space. This mapping is a cube-hypercube mapping done via an ICC colorspace conversion. The cube-hypercube mapping is subject to error. This error is trivialized once the RGB colorspace is in 16-bit. Then the conversion is 48-bit to 32-bit, relegating conversion errors to noise that is below the threshold of vision, or even of the output devices.

    Furthermore, RGB colorspaces almost always have a wider gamut than standard CMYK colorspaces such as ISO, SWOP, and GRACoL. Here again, the 8-bit problem comes into play. When RGB color is converted to a standard CMYK colorspace, the conversion is not really even 24->32 bit, since part of the RGB space is outside the gamut of the CMYK colorspace. Effectively, this means that instead of getting a 256-step gradation in any given channel, you get a smaller gradation, sometimes (for instance in the case of Adobe98 RGB -> SWOP) a MUCH smaller gradation. This leads to stepping problems in gradiants and a loss of detail in images, particularly in shadows. Once more, the move to 16-bit RGB color eliminates these problems.

    So, here's the point: By working in a 16-bit RGB color space, one can effectively do anything that they could in a CMYK colorspace. (Yes, the extra channel is nice for color correction, but not necessary). The final step, conversion to CMYK, has already been implemented in at least two open source engines: ArgyleCMS and LCMS. The conversion to CMYK in an RGB workflow, is the final step. (Unless, of course, you are printing to a lightjet, lamba, etc). The CMYK colorspace that would be used is the colorspace of the output device.

    In professional color, this is not even an issue, for the most part, since most modern RIPs do this conversion for you. 16-bit color support is now starting to become universal in the RIP world. As that happens, the Gimp becomes a viable tool for professional color work.
    • by spitzak ( 4019 ) on Thursday October 25, 2007 @04:12AM (#21110537) Homepage
      You seem to think CMYK is somehow 32 bit (8 bits of each?) and that because 8-bit rgb has 24 bits it can't represent it, but because 16-bit rgb has 48 bits it can.

      This is wrong. CMYK has FOUR dimensions. It is completely impossible to represent it in a 3 dimensional space. You claim is like saying that if I put finer graduations on a ruler, it can suddenly measure 2 dimensions rather than one!

      The converters you talk about (and incidentally are in Gimp already, and in printer drivers when you send them rgb colors) map the 3-D space into the 4-D space. But they cannot fill the 4-D space, any more than you could fill a room with a piece of paper (while keeping the paper's shape a non-fractal). Thus there are CMYK colors that are not output. This has NOTHING to do with color resolution. No useful RGB->CMYK converter will produce both CMY=0,K=1 and CMY=1,K=1 output. Even if the CMYK device was 1 bit per ink and thus only capable of printing 16 different colors, you could not represent all those 16 possibilities with 24, or even 48, or 96 bits, or an infinite number of bits of rgb!

      In reality the highest quality CMYK printing devices available have much less than 8 bit resolution in how much ink they lay down (once you take into account errors in ink delivery and spread). The resolution is so low that the volume represented by the RGB->CMYK conversion is over-sampled by many times when the source is 8 bit rgb. So actually 16 bits does not help one tiny bit in the area you are asking for.

      The reason for more than 8 bits is for processing in the digital realm. For instance if your picture is 1/4 as bright as you want it, and you multiply by 4, then you lose two bits of resolution (as the bottom 2 will be zero). If your screen shows 8 bits and the original was 8 bits, you have effectively reduced your screen to 6 bits. If the original was 16 bits (and your screen was showing the top 8 bits) then after the multiply your screen is still showing an 8 bit image (the top 8 bits of the remaining 14). (that is not real accurate, a correct program with knowledge of sRGB would do something more complex and you would lose more than 2 bits at the bright end, less at the dark end).

      Also more than 8 bits should absolutely use 16 bit half float data. 16 bit integers is a total waste of effort. Float data has the advantage that it is not clamped (this eliminates gamut limitations), and that a vastly larger range of useful data. Even 16 bit data would start to lose resolution on an 8 bit screen if multiplied by more than 256 (actually somewhat larger if sRGB is correctly followed). But 16-bit float would allow a multplication by 65540 or so before there would be loss. The only reason for 16-bit integers was that older computers could not do float fast enough, but this is not a problem now, modern graphics cards even take half-float data directly.
      • by hankwang ( 413283 ) * on Thursday October 25, 2007 @04:30AM (#21110589) Homepage

        The reason for more than 8 bits is for processing in the digital realm. For instance if your picture is 1/4 as bright as you want it, and you multiply by 4, then you lose two bits of resolution (as the bottom 2 will be zero).

        There are other advantages of 16+ bits. 8-bit RGB images are usually in sRGB space, which means that the luminance of a pixel is not proportional to the pixel value, but rather something like the 2.2'th power except for a small range near zero. That is convenient for encoding a large contrast range in just 256 values, but sucks for operations that are inherently linear operators on the luminance, such as background substraction and blurring. With 16+ bits, all operations can be done in linear space without loss of resolution at the darker colors.

Someday your prints will come. -- Kodak