2014.03.24 15:15 "Re: [Tiff] Spot colors in TIFF", by Oncaphillis

On 03/23/2014 10:14 PM, Oncaphillis wrote:

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.

  It seems like the additional information is actually in the "PhotoShop
Image Resource" TAG

(always helps to read the spec.) its stored in the "Alternate Spot Colors" section id=1067

kind regards
Kai-Uwe

Am 23.03.2014 20:37, schrieb Oncaphillis:

Actually for now I just need a way to view the output of my own AGG based rendering engine which should support DeviceN and other kinds of higher dimension colour spaces. If one could point me to another tool that displays this kind of data or to a simple way to generate PSD or PDF from an in-memory bitmap representation it would be highly appreciated.

Sebastian