2014.03.24 13:41 "Re: [Tiff] Spot colors in TIFF", by Kai-Uwe Behrmann
Am 23.03.2014 22:33, schrieb Oncaphillis:
On 03/23/2014 10:20 PM, Kai-Uwe Behrmann wrote:
Am 23.03.2014 22:14, schrieb Oncaphillis:
On 03/23/2014 09:52 PM, Kai-Uwe Behrmann wrote:
With PHOTOMETRIC_SEPARATED + TIFFTAG_SAMPLESPERPIXEL == 4 + EXTRASAMPLE_UNSPECIFIED == 2 (4+2) it would be possible to some a convention.
This is already what the TIFF looks like In addition there are the Spot Color names in the Photoshop Image Resource TAG
In order to display the data a viewer would need a link of a name for the separate colour (say gold + silver) to a actual CIE*Lab value. This can be supplied by a additional ICC Named colour profile (ncl2) beside your normal ICC profile for the Cmyk data. The normal ICC profile is that residing inside the TIFFTAG_ICCPROFILE of the actual IFD. I am not sure how a second named colour profile can be defined inside one Tiff IFD.
Perhaps a completely different Tiff tag is already defined, ready to describe the colorant of the additional spot colour channels.
This could be located in two other Photoshop specific TAGS #700 and #37724.
Are these tags somewhere defined?
It says that #700 hold XMP data. I don't know much about XMP bit looking at it there wasn't anything that looked like they actually sore this kind of mapping there.
#37724 holds the "Adobe Photoshop Document Data Block" which should be described in Photoshop SDK Docs.
Can you provide or link to example files for implementors? I am afraid, I dont have spot colour Tiffs in my collection.