[cairo] Spot colors (and CMYK)

[Bill Spitzak]

This sounds like you want direct exact control over the ink levels.

My proposal is to support it with a "here is the name of the current 
color" api. The back end can use this for any purpose whatsoever. I 
would think this name would literally be the same text that is put into 
the pdf. Other back ends can ignore the name and use the sRGB equivalent 
that is sent at the same time.

This has nothing to do with "color management" in fact it is the 
complete opposite. The sRGB equivalent is not required to have ANYTHING 
to do with the spot color.

Jon Cruz wrote:
> On Feb 18, 2010, at 10:55 AM, Bill Spitzak wrote:
> 
>> In your opinion, exactly what support in Cairo do you need or want?
>>
>> It would seem that you did cms just fine without the need for Cairo to support it, which matches what I think. However I suspect also you are not trying to send exact colors to pdf, which is apparently the main push behind trying to get cms into Cairo.
> 
> Things are a fair bit different that you seem to be expecting.
> 
> Inkscape started without any Cairo at all. Now we've expanded things and are using Cairo for our outline mode. There is also the PDF output extension that now uses Cairo. The main thing we want is to be able to move forward on using cairo everywhere and also to improve the PDF output. 
> 
> One of the big problems we have is with the latter. Most of the professionals who use PDF literally laugh when presented with PDF output from most open source software (Scribus being one notable exception). Inkscape itself can support full CMYK+plus spot, hexachrome, etc. *However* once we export to PDF all data that is needed for any semi-profesionall printing is immediately lost.
> 
> So the key is that we need to be able to get proper n-channel (but not unmanaged DeviceN) output into the PDF so that those who create for hardcopy of one form or another can switch to our software.