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re: Profile utilization test image and profile

MichaelB — Thu, 21 Dec 2006 05:18:48 GMT

Hi Johan,

No, I don't have such an XPS test file myself. The XPS team have a large collection of test files, and may have something along those lines. Email them at XPSInfo@microsoft.com.

Thanks,

MichaelB

re: Profile utilization test image and profile

Johan — Wed, 20 Dec 2006 17:17:23 GMT

On a related note: do you have an XPS test file available that exercises all the different color specifications available for use with both ICC and WCS color engines?

re: Profile utilization test image and profile

MichaelB — Tue, 28 Nov 2006 03:27:58 GMT

Right you are, Charles: it should be "Desmosedici". My spelling checker missed that one :-)

- MichaelB

re: Profile utilization test image and profile

poynton — Tue, 28 Nov 2006 03:15:10 GMT

I think that should be, "Desmosedici" - I don't speak Italian, but I think sedici means sixteen.

Apart from that (!), nice job, Michael!

- Charles

re: WCS Presentation at the 13th annual IS&T/SID Color Imaging Conference

MichaelB — Wed, 22 Feb 2006 23:27:18 GMT

Hi Johan,

Thanks for a good question!

I plan to do a series of posts on the WCS baseline gamut mapping models that will detail their function. Until then here's a brief description of the gamut shells and their usage with the baseline device models.

A device gamut boundary shell is represented as an indexed vertex list of the (possibly convex) hull of the device gamut. The indexed vertex list is stored in CIECAM02 Jab. The structure of the indexed vertex list is optimized for hardware acceleration by DirectX. This approach has many well known solutions (search for "convex hull DirectX" on the web and you get well over 100 hits).

For output devices (displays and printers) we only need to create one shell, the "reference shell". This is because characterization targets can fully span the device space for output devices. For printers we wrap a convex hull around the measurement sample points. For additive RGB devices, we warp the surface of the RGB color cube into the color appearance space and use that.

For virtual RGB devices (i.e. sRGB, wcsRGB) we may or may not have device sample values provided. When the measurement values are available, we generate the reference shell as for output devices. If not, then we warp the surface of a color cube for device values in the range [0.0 .. 1.0] into the color appearance space and use that.

For input devices (cameras and scanners), where a calibration target may not entirely span the device color space, we create a reference shell and a "plausible shell". The reference shell is just a convex hull around the measurement samples used to initialize the input device model. We then use that device model itself to extrapolate color values for the full device color range. Those extrapolated color values are wrapped with a convex hull to form the plausible shell.

Typically, our baseline gamut mapping models apply different gamut mapping in the region between the reference and plausible shells than is used within the reference shell itself.

We have dropped the concept of the "possible shell", as unnecessary for our device models and gamut mapping models.

Best Regards,

MichaelB

re: WCS Presentation at the 13th annual IS&T/SID Color Imaging Conference

Johan — Wed, 15 Feb 2006 14:18:11 GMT

Thanks for posting this presentation. The concept of gamut shells is quite interesting, but it's not enitrely clear to me exactly how they are calculated and exactly how they are used. Could you expand on that a bit more?

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re: Profile utilization test image and profile

re: Profile utilization test image and profile

re: Profile utilization test image and profile

re: Profile utilization test image and profile

re: WCS Presentation at the 13th annual IS&amp;T/SID Color Imaging Conference

re: WCS Presentation at the 13th annual IS&T/SID Color Imaging Conference

re: WCS Presentation at the 13th annual IS&T/SID Color Imaging Conference