[Openicc] meta data in test chart

[Leonard Rosenthol]

On Wed, Jan 26, 2011 at 11:49 PM, Alastair M. Robinson <
blackfive at fakenhamweb.co.uk> wrote:

> On 26/01/11 21:05, Chris Murphy wrote:
>
>  I'm referring to the structure of the PDF. PDF, as far as I know, does not
>> have a means of differentiating between your case 2
>> and case 4. Untagged = /deviceRGB and/or /devicecmyk.
>>
>
> Well I have to say I don't know that much about PDF, so please do correct
> any misunderstandings on my part :)  But as I understand it there are
> different levels of PDF with increasingly complete support for tagging
> objects with ICC profiles?  I see a semantic difference between an older PDF
> with nothing tagged and a newer PDF with objects specifically tagged as
> /device[RGB|CMYK].
>
>
There are 11 different ways to represent color in PDF, and they've all been
around since at PDF 1.3 (Acrobat 4) which is the earliest version anyone
uses today.  So there is no "older vs. newer" issue.

Each graphic object in the PDF can be specified in a different colorspace,
and in the case of paths and text, you can stroke in one colorspace and fill
in another (if you wanted to).

Of those spaces, there are device dependent spaces (DeviceGray, DeviceRGB
and DeviceCMYK), there are device independent spaces (ICCBased, LAB, CalGray
and CalRGB) and there are "special" spaces (Separation, Indexed, DeviceN and
Pattern).


 Leonard
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