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Re: Rendering intents in source profiles?
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Re: Rendering intents in source profiles?


  • Subject: Re: Rendering intents in source profiles?
  • From: Marc Levine <email@hidden>
  • Date: Fri, 25 Jul 2008 10:35:03 -0400

Uli,
The ICC spec allows for different A2B tables to permit users to take an image in and out of that colorspace without changing the original color content. In other words, A2B tables are supposed to be the inverse of the B2A tables. If the B2As are different, then the A2Bs will be different. For example, the gamut compression in a perceptual B2A0 tag is uncompressed in the A2B0 tag. If you transform an RGB image using a CMYK profile and then go back to RGB......


RGB image1->B2A0->CMYK image->A2B0->RGB image2

You would end up with two RGB images that looked very similar to each other.

For an input profile, the A2B0 tag can be used to create a more pleasing image. For example, a digital camera profile cam pump up the saturation and contrast in the A2B0 tag, but have colorimetric data in the A2B1 tag.

Hope this helps.

Marc
--
Marc Levine
Color Management Group Guy
email@hidden



PS: James, thanks for the guidance.

So why are there rendering intents for A2Bn tags, and what do they
actually do? The ICC spec does define separate perceptual,
colorimetric and saturation intents for A2Bn tags (A2B0, A2B1 and
A2B2), and if you test real world profiles as built by e.g.
ProfileMaker, you will find that they do produce different PCS Lab
values for the three intents. But according to which logic??

Thanks a lot in advance for any insight!

            Bye
                    Ul
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