Features
• WCS profiles are NOT compatible with ICC profiles. They are XML-based text files that are much simpler and do not contain gamut mapping calculations at all. Think of them as slightly processed measurement files.
• There are three different kinds of WCS profiles: Device model, gamut mapping method, and appearance model.
The device model profiles contain the color measurement information from the actual graphics device.
The gamut mapping method profile selects which gamut mapping technique the user desires. WCS is based on CIECAM02 appearance modelling.
The appearance model profile contains the parameters for CIECAM02 transforms. This is where you might specify the color temperature of the lighting used to view your print or the color and intensity of its surround.
• WCS and ICM work hand-in-hand in Vista. If all the profiles supplied in a color transformation are ICC-format, then ICM is call upon to do the processing. If one or more of the profiles is WCS-format, then WCS takes over and performs the conversions.
• If WCS is performing the conversions, any ICC profiles in the workflow are converted to WCS format prior to processing the image color data. Any gamut mapping in the ICC profile is ignored and WCS treats it as a virtual device, reconstructing the device measurements from the A2Bn tags in the ICC profile.
• Microsoft has upgraded ICM to version 3, fixed its bugs and updated it to use ICC version 4 profiles, bringing it up to date and hopefully removing any processing problems we've seen in the past. This is great news as it shows that Vista will be able to play with all the ICC profiles in the world and fit into existing color workflows. ICM is still based on the original Heidelberg code.
• Because WCS calculates the color transformation on the fly, gamut mapping should be more efficient and accurate. WCS has the information for each device's gamut and can presumably make better judgements and choices when dealing with out of gamut colors. This also means that black point compensation is automatically handled at this stage. (more on BPC below)
• WCS can also perform calculations using floating point math and allows device models to describe where to map diffuse whites and specular highlights. This and other enhancements allow for a number of new things to occur such as avoiding possible round-off errors on 16 bit devices, support for high dynamic-range devices (like the new digital projectors in movie theaters) and also extended gamuts.
• WCS can also be set to preserve the black channel through a workflow. Something for which ICC users require device link profiles at this time.
• By separating the device information from the gamut mapping and viewing data, users may be able to address specific color problems in the most appropriate area. Gamut mapping issues could be addressed separately from device measurements and viewing issues. In ICC profiles today, all the functions are combined during profile construction into one table.
• WCS can convert WCS profiles to ICC profiles. After conversion, the original WCS device profile is embedded into the ICC profile as the 'MS00' tag. In this manner WCS profiles can be embedded into image files as ICC profiles.
• WCS is only available with Windows Vista and Microsoft has stated it will not be made available to Windows XP.
• WCS was developed in conjunction with Canon.
Microsoft has documented the daylights out of WCS so very little of it is based on 'magic sauce'. Also, many of the algorithm components are extensible or replaceable so developers can write their own plug-ins and alter device models (how the system expects devices to behave, inks to mix, paper to absorb), gamut mapping and so forth.
Microsoft has created a useful demo image that contains an ICC profile that has a WCS profile embedded within it. The image and profiles are constructed in such a way that a Ducati motorcycle appears to be blue, green or red if the profile is entirely ignored, the ICC component is used, or the WCS component is used, respectively. It's worth a look:
<http://blogs.msdn.com/color_blog/archiv … ofile.aspx>
Shortcomings
So, with all these new features and capabilities are there any shortcomings? Well, yes. This is a version 1.0 product after all.
• The WCS CMM essentially has black point compensation ON at all times. In most cases this is good, but if you don't want the blacks intelligently improved - such as when you are proofing - then it means you won't be able to simulate a printing system that has lighter blacks than your inkjet or monitor.
• WCS can handle CMYK devices but at this time there is NO control over CMYK parameters such as total ink limit, black start, GCR level, etc. Laser printers are very different than inkjets which are very different than offset presses. WCS can support different device model plug ins but that is more like presets and I believe there is only one CMYK model shipping with WCS at this time.
• WCS does not support more than 4 print channels. So no Hexachrome or other n-color printing systems.
• WCS, like Windows XP, still does not load calibration curves from monitor profiles. This one deserves a little background...