Linux Color Calibration?

eweaver asks: "Windows has built-in color matching modules like ICM and sRBG, and 3rd-party solutions like Colorific and ColorBlind, but what is the Linux/XFree86 equivalent? Caldera Graphics seems to have some sort of solution, but I don't think it's universal, it seems to work only in their programs. What can I do so that the colors I see in all my Linux graphics apps (mainly GIMP and Blender) are accurate (adjusted for gamma, white point, lighting, etc.)?"

Comments

It's My Understanding..

[Fleet Admiral Ackbar]

that having a good monitor is 90% of the battle. LaCie's "blue" monitors are supposedly very good. A decent monitor shouldn't drift much. I use two SyncMaster 900IFTs, and they match very well, to these eyes at least.

Re:It's My Understanding..

[n8willis]

I use two SyncMaster 900IFTs, and they match very well, to these eyes at least.

Well, in the design world what's really important is that the monitor output matches the printed output; that's what color matching is all about.

Physical systems like Pantone were created so that, for spot colors anyway, we could all know that we were working with the same color because we referenced it with a number, and everyone who had a Pantone swatch book could look at an identical print. So we all have a common frame of reference. Of course, that only applies to spot colors and professional plate printing. With CMYK, even if your printer is Pantone calibrated, you still have to do the proofing stage to make sure the balance is right.

In the desktop-publishing/PC world, the final output is not done by a printing press with Pantone inks, it's done on a desktop inkjet. So specifying a Pantone color doesn't gain you anything, as printers vary wildly in there outputs. Hence the need for software (like Apple's ColorSync) that comes with a vast database of "color profiles" and can automatically map one device's capabilities to another (ie, your monitor -> your printer for prrofs, and then your monitor -> The Big Printer for production usage). It's not providing a common frame of reference, but relative mappings.

I hadn't heard of that Caldera Graphics product; it sounds interesting, but as it appears to have been written by ESL, I'm not sure I'm getting all the details accurately. Any Francophones out there?

Nate

Re:It's My Understanding..

[MikeBabcock]

I hadn't heard of that Caldera Graphics product; it sounds interesting, but as it appears to have been written by ESL, I'm not sure I'm getting all the details accurately. Any Francophones out there?

Yup ... what did you need translated?

Emulation

[buttfucker2000]

Try:
vmware
Plex86
Basilisk

Basically anything that gets you out of X, which is exceptionally primitive, lacking as it does alpha blending, true type fonts, etc., and being useful only for people running software over a network.

I'm not trying to be rude, but if you're going to do graphic design work, you should use a graphics design tool - in other words not X, which is unsuitable - how could you present as work those ugly blocky fonts?

If you want to do anything I recommend a good set of tools - if you're doing cross-country driving I'd recommend a 4 by 4 vehicle - to use a cadillac would be silly, and if you're going to do graphic design work you should use a graphic designer's tool - a Macintosh or Windows.

Re:Emulation

[Stephen Samuel]

Even if Linux doesn't currently have good color calibration software, that doesn't mean that it's not going to. Some people may think that a Mac is the best venue for doing publication work, but SGIs have also been used for quite a while for the same purpose. We can always hope for yet more technology transfer from the SGI world into the Linux world (probably easier than a transfer from the Wintendo/Mac world).

As for the question of "why calibrate": it's mostly for publication purposes. When you're doing up an Add that's going to get 1 Million Dead Tree copies, it's worth spending the time and money to make sure that the soft blue hue isn't going to come out light navy (worst case).

For stuff that's going to get 1 million Dead Electron (Video) impressions, there's no way to make sure that the color on your screen is going to be seen exactly the same on another screen. On the other hand, if you have a (reasonably) well calibrated screen, there's at least some hope that things won't be as far out on average.

Example: If you're calibrated good, and I'm dark, your work will seem no worse than most other good images. On the other hand: If you're calibrated light and I'm calibrated dark, your image may still stand out as noticibly bad on my (already improperly calibrated) video screen.

If you're the only person who's going to see your graphics work, then calibration isn't terribly necessary. On the other hand, simple calibration will make it easier to match stuff from your scanner and it's usually nice to know that you're seeing an image in somewhat the same colors as was intended by the artist that created it.
`ø,,ø`ø,,ø!

Re:Emulation

[GypC]

You really like to talk about things of which you know nothing, don't you?

Try using the Gimp to create a banner... use some True-Type fonts (which, by the way, work fine with older versions of X as long as you have a font server that supports them, like xfstt). OK, use the text tool, type in your message, press OK.

Oh look! Those letters in the image are antialiased! Gee, what a suprise, and here I was thinking that buttfucker2000 knew his ass from a hole in the ground.

Look, dipshit (and I wouldn't be so rude if you weren't obviously either a liar or a parrot), X can't antialias fonts that it draws directly (because the X protocol treats fonts as a 1-bit mask), but any application can take the task unto itself and antialias whatever the hell it wants to.

"Free your mind and your ass will follow"

Re:Emulation

[Tet]

For stuff that's going to get 1 million Dead Electron (Video) impressions, there's no way to make sure that the color on your screen is going to be seen exactly the same on another screen.

Of course there is. That's why graphic formats like TIFF (and nowadays, PNG) let you include a colour profile, precisely so that the image does look the same on all screens. Of course, if the target monitor isn't calibrated in the first place, then no amount of colour profiling will help, but the intentions are good... With the world apparently moving towards sRGB, hopefully this will become less of an issue in the future.

Re:Emulation

[ianezz]

• lacking alpha blending: alpha blending (and font antialiasing) can be easily done by the user apps that require it - having the support directly in the X server is nice and desiderable (XFree86 4.x implements such extensions, so toolkits like Qt or GTK+ can start using them and providing nice API), but absolutely not required (The Gimp does alpha blending and antialiasing by itself, the same is true for Gnome Canvas and Swing of Java memories).
• true type fonts: come on, please! There has been True Type font support for ages through appropriate X font servers. And you can easily have them along with Compugraphic fonts and the usual Adobe Type 1 (and more esotic sorts) by simply using an X font server. And graphic applications can smooth them by themselves (i.e. The Gimp, apps using the Gnome Canvas widget, GhostScript when rendering PostScript text, or Acrobat Reader - they all use antialiased fonts and graphics where they are required).
• how could you present as work those ugly blochaveky fonts?: come on, please (again)! You can have all the vectorial fonts you want (even a hight-quality edition of the 35 standard PostScript fonts, search on Goole for URW fonts, but if you have GhostScript you probably have them already), and graphics programs can do antialiasing by themselves.

That said: X is not the best at everything, and color calibration is one of these. If there is enough interest, it will be implemented as an extension to the X protocol. Instead of bashing X, go after X implementors, like the XFree86 group, and ask or help them to properly design and implement such thing. Then you'll have fine color calibration in X.

Re:Emulation

[Nailer]

Your a troll. I'm biting.

*
Alpha blending is being worked on by Keith Packard of SuSE inc. and the brilliant XFree86 team, and should be implemented in a future version of XFree86

* True type fonts have been around for over 2 years and are standard on all major distros. XFree 3 uses an external font server like xfstt, XFree 4 handles them natively.

* etc? True, X lacks color correction. But XFree 4s modular interface allows for a companys to sell closed source X modules AFAIK, so an Apple ColorSync module should be possible. Why not do something constructive and mail them about it?

Re:Emulation

[nathanh]

Basically anything that gets you out of X, which is exceptionally primitive,

Oh really, let's see why you think this...

lacking as it does alpha blending,

Xrender does this, and it is an X11 extension.

true type fonts,

XFree86 4.0 supports TrueType and Type-1 fonts.

etc., and being useful only for people running software over a network.

All shared resource systems need some form of IPC between the clients (many) and the resource (single). In Windows this is message passing. In XFree86 it is named pipes. Named pipes are more primitive (and faster) than message passing. X11 is not slow. This is a MYTH.

The problem is that people confuse windowing systems (many clients, 1 framebuffer) with games and other direct rendering problems (1 client, 1 framebuffer). They conclude that any windowing system which can't perform as quickly as a plain framebuffer is "broken", "stupid" or "only good for networked graphics". This is plain wrong.

For direct rendering, which is where you have a single client and a single resource, then the highest speed is achieved by locking the resource and performing Direct Rendering. You might have noticed that Windows only recently offered direct rendering as a feature: years after SGI offered direct rendering for OpenGL over X11. XFree86 now offers two forms of direct rendering: DGA or DRI.

We have the fastest possible IPC for indirect rendering (named pipes) and the fastest possible methods for direct rendering. So why is there a still pervasive myth that X11 is broken? Display Postscript, Direct Rendering, OpenGL, Type-1 and TrueType fonts... WHAT MORE DO YOU WANT?

Sure, X11 isn't perfect, but this is because it's a non-trivial system and it certainly seems people prefer to whine about it rather than help out in development.

If you prefer to do things, rather than talk about it, then go to www.xfree86.org and join up for development. There are many things that need to be done and far too few people working on it.

Re:Leave color calibration to desktop publishers.

[h_jurvanen]

Seriously, why do you need to calibrate your color?

It's probably a desktop publisher that's asking the question! If Linux advocates want it to be accepted past its current geeky bounds, it is going to have to start incorporating features used by people from other walks of life.

Herbie J.

Color calibration

[Mickey Squid]

I manage a prepress department where color issues and color calibration are very important. The Mac and to a lesser extent Window have color calibration built into the OS. I don't know of any ICC profiling or calibration for Linux, but I haven't used Gimp in a while either so I don't remember. In any case an ICC profile or other file for monitor calibration is only the first step and lacking built in profiling you can alway purchase a monitor which has this ability built in. Some on the Mistubishi monitors for example. Understand that any time you change the lighting in your room recalibration will be required in order to maintain absolute color accuracy. You probably don't really need this accuracy and I recommend that you get a monity wich gamma correction built in, create a graphic with lots of colors in it (the more diversity of color the better), take that graphic on disk (or ftp) to a graphics service bureau and have them output a digital on their color corrected equipment. Put your room in the most commonly used lighting setup, hold your digital next to your monitor and adjust the gamma correction settings on you monitor until you get pretty good match. It is better to go a little dark that a little light. Paritcilary watch the reds and the blues. Also remeber that Gimp uses the RGB color space exclusively and the digital is output on a CMYK printer which has a smaller color space (is capable of fewer colors). When you get a good match between your digital and your monitor you are 95-97% as accurate as the big boys with thousands of dollars worth of color calibration equipment.

Re:Color calibration

[cfish]

The problem with this approach is that you colibre your monitor relative to your printer. i.e. trusting that your printer is correct.

While nearly nothing is absolutely correct, and not many people need them to be correct anyway, I think the stone age method still apply - get a little booklet of Pantone colors and compare it directly with the computer.

As a programmer and a graphics designer, I must say, I have my linux box contrast adjusted to really low because i need the text to be crisp. Programmers need crispness 100 times more than correct colors.

XRainbow

[ElfMagic]

I recall kate fenton (katedown@hotmail.com) from SGI coming up with an app called xrainbow last summer that did exactly this, however I cannot find the url to the project's homepage. You might try contacting her about it..I contributed a bit of source to this, but I cannot for the life of me find the source nor binary..I'll continue to look and post a url to the source when I find it..it's gotta be on one of 300 or so cd-rs laying around here :)

XF86 will have to ditch XF86Config first.

[AFCArchvile]

Seriously, that could be retooled into one standardized control panel. In other OSes, it is not necessary to enter in the horizontal refresh rate if you already know the vertical refresh rate; the horizontal refresh rate can be calculated if you know the vertical.

Also, it would be nice to be able to adjust the resolution of X while actually in X. When you tweak with the XF86Config in vim and then try to start X, only to have it terminate because it doen't like one line, it just becomes so exasperating.

In short, Windows has a GUI display control panel, MacOS has a GUI display control panel, so why doesn't Linux have one yet? They've only had about five years to make one, so there's no excuse.

Re:XF86 will have to ditch XF86Config first.

[GrenDel Fuego]

That only works if you have multiple resolutions defined.

I personally only define the one resolution that I generally use due to X automatically changing the virtual desktop space to the higest of the defined resolutions.

If I want to change my resolution, I think that the desktop area should be changed right along with it. I know not everyone would want this, but it should at least be an option!

Some info

[raph]

A fair amount of info on color management tools is on my color management page. One of the most exciting pieces of technology is the Argyll color management system.

The main thing that's lacking right now is integration. A lot of the pieces exist, but they're tied together yet. I plan on integrating Argyll into Ghostscript over the next few months, so that's likely to be a good start.

Interestingly enough, X had a very good start at a color management system (XCMS). However, as far as I know, nobody ever used this seriously, so it's yet another hunk of worthless junk hanging off the X server. This type of thing still "works", though:

xterm -fg CIEXYZ:0.371298/0.201443/0.059418

Of course, the chance of your monitor actually matching the CIE color is pretty close to nil.

In any case, there's quite a bit of work underway, and it's reasonable to expect that Linux will eventually have good color management. If you want it sooner rather than later, contribute to one of the projects!

Color calibration- why bother?

[solios]

There's really not much point to it in linux, and there probably won't be a demand for it for quite some time. Seriously- how many Linux / UNIX users use their systems for graphics? (I would be interested to see what IRIX has in the way of calibration utilities).

If you're looking to do serious graphics work and monitor calibration is a MUST, forget linux and Windows. Macintosh has lasted this long because of colorsync and the fact that Photoshop seems to run a hell of a lot smoother on a RISC processor. If Adobe, Macromedia and Quark ceased support for the Mac, Apple would be a ghost within a year.

The Mac was DESIGNED for content creation, with a huge emphasis on making the UI a tool for the artist instead of an obstacle.

Windows has become more of an entertainment medium, and IRIX handles the super-high-end 3d on the SGI systems.

Linux does everything else quite nicely, but as a SERIOUS graphics tool, it's a joke. Until either X gets a boost or a better open-source / free windowing system comes along, accept the fact that Linux simply can NOT fill EVERY need for EVERY person who uses a computer in the course of a days work.

Everything has to negotiate

[Anonymous Coward]

The main advantage of color calibration is not just so that your monitor can agree on a color with whatever piece of paper or other display you're comparing it to (exactitude is impossible for a number of reasons). The main advantage is that your various devices can agree with each other; so that the color shift on your monitor is compensated for RELATIVE to your cheesy ink-jet printer as well as the printshop across town that's managing the color seperations. (and, likewise, the files created by your various graphics programs agree on color values relative to each other; color management is much more surreal than it seems like it should be)

Apple's ColorSync absolutely rules at this because it's platform-wide and any user can build a new color profile. Frankly, if the various X graphic apps could do color management right, Linux/Unix could become a serious graphics platform. Well, that and font/bezier antialiasing. And featureset parity. And so on. But it'd be one of the major hurdles to overcome, even if it's one of the least sexy.

Most hackers think of 3D when they think of graphics, but the vast majority of the graphic design community's bread and butter is 2-D work; page layouts, photo work, and so on. I could make a small 3D animated movie on my Linux-only laptop, but i couldn't make a business card for a client.

There is an old saying. . .

[kfg]

Used by athletes, martial artists, and even musicians.

Rely on your strengths, WORK on you weaknesses.

Linux is not *a* tool, but rather a collection of tools. It's silly to say the toolkit shouldn't be expanded and refined.

What's more, it is in the very nature of Linux to at least attempt to be a jack of all trades, since it is made up by the users themselves.

Graphics capabilities are the major weakness of Linux in the field of modern OSes. This is not inate to Linux, it is a FLAW that can be fixed without any degradation of any of its other useful functions.

What is Linux REALLY good at? Anything we as a group can code for it. THAT is the whole point of Linux and its only real strength.

Re:It's not a major priority now

[garcia]

I have not used Photoshop on a G4, but I have used it on PowerPC's and G3's. It is NOT faster than my k6-2 350 or my 500+ (OC'd to fit in the 133mhz bus). In fact, it crashes a lot and it is rather annoying.

that is just my observation...

No excuse - it's open source!

[Midnight Ryder]

In short, Windows has a GUI display control panel, MacOS has a GUI display control panel, so why doesn't Linux have one yet? They've only had about five years to make one, so there's no excuse.

Ya know, you are right - there is no excuse for the fact that there isn't a control panel. For the last however long, Linux users have lived without a control panel. Since Linux (GNU/Linux, whatever) is an Open Source project, and the same with the WMs running on X, etc., it means that until recently, no one felt the need.

However - you feel the need. So, go build it. That's what it's about - contributing when you feel the system is lacking something. Have an itch? Scratch it, and submit the code. Go build one for Gnome or KDE. Don't give the excuse you aren't a programmer - here's a project to cut your teeth on. And I can't belive you don't have the time to do it - I've now seen this exact statment from you twice. The tools are free, so money isn't the issue.

So, basically, put up or shut up - if you want it, build it. That's how it works in an Open Source project. You won't see my name on any of the Linux projects - I've yet to feel the need for something within Linux (however, I have helped out on a couple other OS and free software projects. I just happen to have different itches to scratch.) Seriously - take up the project, design it, implement the inital code, and release it on the world - that's what it's all about! :-)

Re:No excuse - it's open source!

[Mr. Slippery]

And what about those who have the time but don't have any interest in learning the intimate underpinnings of the computer?

They can pay someone to do it. They can either pay a vendor who won't open the source and will lock the customer into their proprietary system (and maybe even lure them into a subscription system), or they can pay someone to develop an open source system, possibly via a market like SourceXchange or CoSource.

Actually X can do it all!

[Wills]

As I posted below, the whole point of the color calibration stuff in X is it can handle color in a device-independent way by using CCCs (Color Conversion Contexts) to specify a display's color pecularities. Do your own monitor color calibration and simply load the calibration data onto your Xserver using xcmsdb. Once you've done that your example of specifying a device-independent foreground color in xterm using the CIE XYZ color space would give a properly calibrated color on your monitor. That's pretty useful. Your criticism of color management in X is inaccurate and misleading because you don't understand how to use it properly.

As a footnote, doing an accurate color calibration of a monitor, requires expensive test equipment like a tele-spectrophotometer.

Re:Get a Mac.

[Stephen Samuel]

From X --help:

-cc int default color visual class
-co file color database file
...
-gamma f set gamma value (0.1 < f < 10.0) Default: 1.0
-rgamma f set gamma value for red phase
-ggamma f set gamma value for green phase
-bgamma f set gamma value for blue phase

I don't use them personally, but I'm sure that people can come up with tools that would make using these (and other X color support features) easy for non-geek pre-production types.
`ø,,ø`ø,,ø!

Re:Font smoothing

[Dr. Evil]

In one of your other posts, you mentioned banner ads without font smoothing/antialiasing. The GIMP does antialiasing. As for colour matching, I never had a need for it, but I never did professional publishing. When I need colour accuracy, I paint by numbers.

I see the lack of Truetype as a greater impedement to amateur desktop publishing. Truetype is excellent for people who care about what their work looks like while they're making it, but it is not as good as other font formats for the final output (Think small caps, character kerning etc.). And Linux, unlike Windows 3.1 doesn't support Truetype, it supports hacking truetype into an X-like font, or rendering truetype on the screen, but linux, unlike Windows 3.1 has no underlying printing architecture.

Read up on why Abiword uses Truetype under Windows, but not under Linux for more information:

http://www.abisource.com/faquser.phtml #2. 7

Besides, with no printing architecture (which I believe Gnome is working on correcting), you certainly couldn't do ICC on printers anyways.

http://developer.gnome.org /ar ch/imaging/printing.html -- I hope somebody's touched that since its September 1998 date.

That about exhausts my knowledge of printing, fonts and graphics. Some day I'll have to get my hands dirty on these projects.

Look for the Union label

[underwhelm]

Make sure that any color-matching plugin you use has Squant support.

Color Calibration fun...

[greenfield]

There has been some discussion about using nice monitors to get good color calibration. Unfortunately, good monitors are not the only issue. A good monitor may produce more precise color for a longer amount of time, but it may not be accurate. (Very few monitors are self-calibrating.) The idea behind color calibration is produce color that is both accurate and precise across a variety of devices.

The idea behind color profiling is that each device you use, input or output, has a profile. This profile allows you to take an image from the device specific color space to a neutral color space, such as XYZ or CIE Lab. Some devices come with profiles from the manufacturer, but if you want to get serious about color profiling, you must create your own profile.

One way to create a profile for a monitor is to buy a program that profiles your monitor using a colorimeter that you attach to your screen. For a printer, you can print out a series of color swatches and then scan in all of the color swatches with a colorimeter. (In short, a colorimeter is a very accurate color scanner.)

For example, say your monitor always has a bluish tint. When you profile your monitor, the colorimeter will "see" that more blue is always coming out of your monitor. The ICC profile that gets generated will have values that de-emphasize blue. Thus, when you install your ICC profile on Windows 98/2K or MacOS, the operating system will apply this profile to all images and colors generated from the screen and a more accurate color will be generated.

Printers are also interesting with respect to ICC profiles. Color printers are generally CMYK devices--not RGB devices. CMYK stands for the ink colors Cyan, Magenta, Yellow, blacK. ICC profiles for printers will convert to and from CMYK colors.

Color can be a tricky issue--I'm really glossing over a lot of important details. If people are interested in this issue, then can send me mail and I will try to dig up a reference or two.

Of course, what would a Slashdot posting be without some unsolicited advice? Most monitors come from the shop with the brightness all the way up and the color temperature at 9000 degrees Kelvin. This "looks good" the same way loud music "sounds better." Set your monitor to 6500 Kelvin or 5000 Kelvin and turn down the brightness significantly. Your monitor may seem more brown or yellow, but in reality it is a more neutral white. After time, your eyes will adjust to the newer whites and you will be happier. Also, if you turn down the brightness on your monitor, it will last longer!

Re:It's not a major priority now

[NMerriam]

There are no REAL professional graphic designers or publisher that use Windows either.
They use macs because of ColorSync and because Photoshop actually runs much much better on macs.

Son, REAL professional graphic designers don't need colorsync, so it doesn't matter what OS they're on. If you don't know what a CMYK value is gonna look like without help from colorsync, you're not going to know WITH it, either.

Postscript is platform-independent, I've been using Windows for publishing ever since 3.1 (there was a time when any serious photoshop people were using OS/2 Warp to run Photoshop 2.5 because it was the most stable and memory efficient configuration on ANY system). I've meet plenty of Mac folks who don't believe it, but I've never met an imagesetter yet that disagreed with me...

---------------------------------------------

Calibration for visual effects

[rogerbo]

Linux is used by graphics professionals just not a lot in print yet. But in visual effects and in particular film visual effects, linux render farms are already common and linux graphic workstations are becoming increasingly common.

Most large visual effects houses have inhouse calibration tools that match monitor LUT's (look up tables) to film recorders so they are sure what they see on the monitor is what goes to film and gets projected.

An Australian company Rising Sun Research has just released CineSpace which is available on linux / irix and windows nt/2000. Never seen it so can't say anything about it but it's available here:
https://research.rsp.com.au/index.cfm

Java has excellent color management

[Olentangy]

The Java 2D API has excellent support for color management (I believe the code in the JDK is from Kodak) and can use ICC profiles. So Java programs running on Linux can have excellent color control.

See: http://java.sun.com/produc ts/ java-media/2D/index.html

-- michael

How about color _separations_?

[DG]

While we're on the topic, how about doing CYMK 4-color separations using Linux?

Can Ghostscript do this for you, or is this an end-user deal?

Links and advice highly appreciated.

Re:How about color _separations_?

[snowbike]

dvips will let you do this. From page 349 of the LaTeX Graphics Companion (great book!), the command to make the magenta postscript from a file called image.dvi is:

dvips image -h aurora.pro -h magenta.pro -o image-magenta.ps

Try kvidmode!!

[Moritz Moeller - Her]

It allows you to at least set the gamma mode of your display in KDE2. I use it, it is still in it's infancy, but at least a start.

Check it out at http://apps.kde.com/infofr.php?id=837Looks nice and might evolve to something great... I like it

Quick link

[omegawolf]

A quick search for "Linux color management" on Google led me to this web page.

Like the original poster, it appears this person has yet to find a solution, and may be starting a project.

To those that question the need, it truly is there. I'm a graphic designer by trade, and it is a major issue. Macintosh users (such as myself) have plenty of CMS resources, but I have yet to hear of anything for Linux.

From long experience ....

[taniwha]

I used to design graphics accelerators for Macs. Color fidelity/matching/whatever was a very big issue - marketting was very hot on it and we worked hard to do 'the right thing'.

The problem is that you can't satisfy everyone - even though you might be able to get it close to 'right' for one person everyone's eyes are different - the numbers of rods and cones vary widely enough that the way we perceive colors from phosphors and reflected from paper is different enough from person to person that you can't get it right, just close (for example at one extreme is the 10% of the male population who are red-green color blind).

Another example of this is the way that ambient light plays in our perceptions - colors can look totally different in the morning than in the evening in the same room because the color composition of the ambient light changes - people in publishing who are serious about this sort of stuff have 'white rooms' with known lighting and no outside windows to look at stuff in.

In my experience this area is enough of a sinkhole that you can/will get lots of competing schemes for color matching with lots of area for arguing - IMHO any color calibration system that doesn't calibrate for the individual user's eyes is worthless - but at the same any system that does so is so subjective that it can't be reliably measured.

Oh yeah - and look very closely at any system that performs liner math (multiplication, matrix ops etc) on gama corrected (logrithmic) pixels [hint almost any HDTV system that does picture scaling does this]

Raph, interesting patent stuff there...

[Svartalf]

Went to your color management page, looked at the potential patent issues info referenced and have some comments that are germane to the discussion that you've started here. (And we ought to use the /. effect for good purposes in this situation... :-)

The Schriber patent (US4500919) seems extremely overbroad- may or may not be valid and seems to describe something slightly different than what we're looking for in a calibration system upon a detailed reading of what is exactly claimed in the patent. May apply, may not. Expires sometime in 2005 in any case.

The Walowit patent (US4941038) should probably be overturned- I've some nagging prior art suspicions on this one as it simply describes a system that does RGB to CMY conversion, adjusting for gamut differences in the original image and the target environ. (Now, where do I remember seeing code for that... Perhaps this one should be submitted for a bounty.)

The Arazi patent (US5212546) looks to be obvious (verging on common sense) and I'd think that it'd be covered by prior art anyhow (Wasn't Kodak or Fuji doing this sort of thing years ago, prior to the patent grant?)

(By the way, you might want to change the URLs to refer to 'http://www.delphion.com/' instead of 'http://www.patents.ibm.com/' as IBM's basically given the services to the Delphion IP Network...)

I don't understand why this is important.

[DunbarTheInept]

I've seen these alleged color correction tools in Windows before, and I've always wondered what the point of them is. Who needs them? In what business or field of study (or video game) does it really matter that the color and gamma match exactly to what was intended? As long as they are close enough (i.e. magenta doesn't end up looking like green or something), then who cares? People are going to adjust their monitors anyway to match what the like to see, so the whole notion of gamma correction in software is pointless, as far as I can tell. In fact, I made the mistake of installing one of these things that came with a video card I bought, and now my games are all fu'bared and I can't adjust them back the way I like (and the tool didn't come with an uninstall option, so gettting rid of it will probably take some icky registry hacking as well as just deleting the files.) Is there some field of study or business I'm unaware of that really needs this kind of tool?

I'm not trying to be flameful - I'm genuinely confused. Obviously a market of some sort exists for these tools or they wouldn't keep making them, but I can't figure out what that market would be.

Re:It's not a major priority now

[NMerriam]

as opposed to a quiche eater?

I meant as opposed to folks on slashdot who "do a little work in Gimp now and then" or "I used to work on the school paper, and we used all macs".

i dunno about you but my years of working in the advertising and design industries brings me to the conclusion that Mac rules well beyond all others

Oh, certainly in numbers, Macs still are far ahead in the industry. My personal feel is that it has more to do with inertia than anything -- the same reason a lot of folks here say "oh, to do graphic design you need to use a mac". It's just "common knowledge" that you use macs for prepress, because of the historical development there.

As for OS/2, unfortunately it was only a year or so that it showed so much promise. We converted a LOT of systems to Warp when it came out, so that we could run photoshop on it, and it was fantastic -- I remember the Adobe Forum on Compuserve went nuts when PS3 came out because it wouldn't run on OS/2, and we kept begging IBM to get a win32 system going. The history that COULD have been, I suppose!...

---------------------------------------------

Color calibration pisses me off

[Adam Wiggins]

Color calibration annoys the hell out of me, and I'll tell you why. Artists (and I've worked with many of them due to my years in the game industry) all think that it's their job to make sure their art looks the same on everyone's monitor. They think that if someone has their brightness turned down or otherwise has different color settings than wherever they originally created the art, that it looks "wrong."

Here's my complaint: the reason that you *can* change your monitor settings is that everyone has different eyes! My eye doctor always notes that my eyes are unusually sensative to light. When it comes to adjusting my monitor, I always want my brightness way down and the contrast at maxmimum. People always comment that they think things look "ugly" on my monitor because they are dark and high contrast; but I think that the settings that most people keep their monitors at are ugly because the colors look washed out and all the blacks look like dark grey to me.

There are a few places where color calibration is most certainly relevant (such as when your final medium is not a monitor, but a piece of paper, or something else), but most of the time you should just get it the way that you want it to look on your monitor and not worry too much about it being exactly identical on other monitors. (I do usually try viewing my web images with the brightness on my monitor turned up just to make sure that the blacks aren't too grey, but that's about it.)

Here's a question: anyone know how to turn off the use of gamma on a PNG? I love png's (smaller and more color depths than gifs) but IE and Mozilla both use the gamma setting and it ends up looking totally different from Netscape or a non-gamma'd GIF, even on the same monitor. My only solution so far has been to save the image as a PNG, quit the gimp, edit .gimp/gimprc to set gamma-correct equal to 0.4, restart gimp, load the PNG, and then save it out again. This results in the image looking pretty close to its original colors (that is, how it would look if I had just saved it as a GIF), but it's not exact. This issue is especially important when you're trying to make your image colors match that of the HTML-coded colors on your document.

Re:Color calibration pisses me off

[Glenn R-P]

Here's a question: anyone know how to turn off the use of gamma on a PNG? I love png's (smaller and more color depths than gifs) but IE and Mozilla both use the gamma setting and it ends up looking totally different from Netscape or a non-gamma'd GIF, even on the same monitor. My only solution so far has been to save the image as a PNG, quit the gimp, edit .gimp/gimprc to set gamma-correct equal to 0.4, restart gimp, load the PNG, and then save it out again.

pngcrush -replace_gamma .4 -ext _g04.png *.png

If pngcrush isn't already on your system you can get it from
pmt.sourceforge.net

there is no "accurate"

[q000921]

While color calibrationists are pushing the idea that there is some ideal notion of "accurate" that monitors can be made to conform to, the reality is much messier: color perception depends intricately on context, monitors cannot even begin to match the visual experience of real pigments and dyes, a wide range of "calibrations" are visually acceptable, and different people have different preferences and perceptions.

So, what should you do? Often, you can work reasonably well without more than a rough calibration. In fact, most critical color correction can be done completely in black and white--matching known colors (logos, skin color, neutrals) correctly is actually better and much more accurately done numerically than "by eye". Once you have established those anchor colors, you have a visual context, and you can fiddle with the other, less specific colors around them by eye without worrying too much about monitor calibration.

For on-line applications, you need to worry even less: none of your colors will display "accurately" on most machines anyway. You simply have to make sure that your images look OK on "average" PCs. While having a consistent starting point for designing those kinds of images is kind of nice, most good graphics cards and good monitors are probably going to be "in the ballpark" if they are reasonably well set up.

Maybe you really do need calibration for some of your applications; I have occasionally needed it for some really obscure work. But I think in many cases people want calibration for all the wrong reasons: for print work, calibration isn't accurate enough, and for on-line work, it doesn't help you much.

Color correction and dot gain

[psyklohps]

I work at a local newspaper doing page layout and graphic design. Let me tell you that color correction and dot gain are very important.

An explanation of dot gain is how much more or less saturated the color is going to be from the start of a project to finish. Lets say that you get an ad from a customer. First you need to turn it into an EPS from a PDF, then you print it to negative, burn the plate and then ink the plate and press it to paper. We have a 30% dot gain. That means that an area that is 70% black on the computer screen will be 100% black on press after all of the conversions; consequently 30% black will be almost white. If you can see what the colors are going to look like accuretly on screen then you will get a better printed product.

One time I worked on a project at home using the GIMP (RGB only) and then taken it to work, after the conversions to CMYK and the dot gain, the image looked like shit! So I only use the GIMP for web graphics. That really sucks because the GIMP would be a graphic powerhouse if it supported CMYK and if I could color correct X properly.

Now if we could only convince Quark to port Express and Macromedia to port Freehand I would never touch a Mac again.

For those who still don't get it

[FIGJAM]

This link might make you think of either how crapy your monitor is and/or how much color correction is necessary.

Re:Font smoothing

[Dr. Evil]

Not quite true. Most applications use the printer driver to optimize the output. While it is confusing and it rather sucks, it makes more sense to have the printer say "I have an internal font which represents this TrueType font as though it were a postscript font."

It also makes a difference for various resolutions. 150dpi will print characters better with particular properties than than will 180, 300, 360, or 600 dpi.

Tack on other limitations such as the printable area and it makes sense that the document will reformat itself for the printer.

If you take several reasonably well written printer drivers for printers genuinely capable of printing the same resolution ( 300dpi doesn't mean each pixel is 1/300th of an inch. ), and you disable font substitution and other similar printer based enhancements... or if you simply run the printers in compatability mode (using the same drivers), then you will not have this "problem."

If you want the same thing output every time regardless of the person's machine (scaled down depending on the printable area) use a PDF. You can also use a generic postscript driver and Ghostscript... the same way that Linux prints.

gcms

[heby]

at least for printing there is gcms, the generic colour management system... check out http://gcms.sourceforge.net

Re:Micro HOWTO on color calibration in X

[Raphael]

These messages mean that your display is not calibrated (no color-correction matrices have been loaded). If you get these messages before loading any profile (e.g. with xcmsdb sample2.dcc), then this means that your X server starts without any specific color characterization data for your device, but it does not mean anything regarding whether or not it supports this feature.

If you get these messages from xcmsdb -query after loading one of the example files such as sample2.dcc, then it is likely that your X server does not support color calibration. You should upgrade to a more recent version, if available... If you are using a commerical server that you cannot upgrade easily, then you should report this problem to your vendor.

For example, when I start a new X session (server: Sun OpenWindows 3.6) and I run xcmsdb -query, I get a message telling me that there is no XDCCC_LINEAR_RGB_MATRICES property, but there is already a XDCCC_LINEAR_RGB_CORRECTION property, containing RGB conversion tables for the visuals of the display. Some other servers (XFree86 3.3.6) start without any color characterization profile.

After running xcmsdb -remove on any display (regardless of the version of the X server), then I get the messages:
Could not find property XDCCC_LINEAR_RGB_MATRICES
Could not find property XDCCC_LINEAR_RGB_CORRECTION
because the profile has been removed.

When I run xcmsdb sample2.dcc followed by xcmsdb -query, then I get something like this (long tables snipped):

Screen: 0

Querying property XDCCC_LINEAR_RGB_MATRICES

XYZtoRGB matrix :
4.07591 -1.82044 -0.62731
-1.10248 1.93518 0.03736
0.05997 -0.20679 0.88572

RGBtoXYZ matrix :

0.33330 0.33724 0.22183
0.18946 0.70614 0.10440
0.02167 0.14203 1.13838

Querying property XDCCC_LINEAR_RGB_CORRECTION

VisualID: 0x0
type: 0
count: 3
Red Conversion Table:
length:256
0x0 0.00000
0x101 0.00000
0x202 0.00000
[...]
Green Conversion Table:
[...]
Blue Conversion Table:
[...]

If you get something similar, then your server is working fine. If you still get an error, then you should complain to your vendor.