[Openicc] meta data in test chart

[Chris Murphy]

On Jan 24, 2011, at 5:57 AM, Graeme Gill wrote:

> 
>> The system above is actually not a bad design, but it would be even
>> better provided the handoff space were ProfotoRGB (very wide gamut)
>> or PRNG (all printable colors), and a 16 bit conversion were
> 
> I'm not sure that's a good idea with current workflows. The reason
> is that few if any workflows have, or communicate the concept
> of an image gamut. Unlike other smaller gamut color spaces, where
> typically the image has been rendered to just fit into that space,
> and therefore the colorspace gamut is a reasonable guide to the image gamut,
> a very wide gamut space like ProPhoto or L*a*b* cannot be used
> as a guide, because the images gamut will almost always be a great
> deal smaller than the space it is encoded in.
> 
> The reason this is important is gamut mapping. If an image is to
> be mapped well into the destination colorspace, the gamut it
> occupies needs to be known or anticipated. If the encoding colorspace
> no longer provides that information, where does it come from ?

Use of the PRMG would be useful here, in theory, because the idea is that the image is rendered scene-referred to output-referred once in something like ProPhoto RGB. The problem is that Adobe RGB and ProPhoto RGB do not come in v4 versions that make use of the PRMG. And then also there are no widely available v4 + PRMG output device profiles. So as far as I'm concerned ICC v4 and the PRMG are in a coma for mainstream users.


Chris Murphy