Re: YCbCr
Re: YCbCr
- Subject: Re: YCbCr
- From: Rolf Gierling <email@hidden>
- Date: Thu, 28 Jun 2007 11:08:49 +0200
Hi Graeme,
this is not quite correct, although there is no doubt on what you're
saying.
The profile I was refering to that comes with Adobe Photoshop is used
by the Kodak Aquire plugin to convert their Photo CD image format
from YCC colorspace to anything else.
True is, that they decode the file first, as the encoding is propetary
and not published until today.
cheers
Rolf Gierling
Am 28.06.2007 um 05:35 schrieb Graeme Gill:
In principle there is no problem with this, in practice the ICC
standard lets you down. While it defines a colorspace tag for YCbCr
space,
there is no encoding standard, so you can't be sure how (or even if)
a CMM can handle native YCbCr in a way that is consistent with the
image
encoding, nor know how to create a profile that will be consistent with
a CMM. It would be possible to build a closed system that
worked (ie. by making sure that the image processing and profile
encoding for a YCbCr colorspace matched).
I seem to recall one comment about this last time it came up,
along the lines that "no one uses profiles on YCbCr space directly,
they apply them to the RGB transformed version of YCbCr" or
some similar statement. This doesn't solve the problem of gamut
mapping to/from the actual YCbCr gamut though, since the gamut is
hard to identify when represented as RGB.
If there was a standard way of encoding YCbCr device values in ICC,
then there is then nothing to stop you creating a reasonable
gamut mapping between that and an RGB space, if you use a
suitable source/destination gamut mapping capable ICC linker (ie.
Argyll).
Graeme Gill.
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| References: | |
| | >YCbCr (From: "Scott Ettin" <email@hidden>) |
| | >Re: YCbCr (From: Graeme Gill <email@hidden>) |