[Webkit-unassigned] [Bug 12205] Add support for CMYK for css colors

bugzilla-daemon at webkit.org bugzilla-daemon at webkit.org
Fri Jan 12 06:38:12 PST 2007


------- Comment #6 from contact at nickshanks.com  2007-01-12 06:38 PDT -------
A reply from Håkon:

> Could you provide any details on the CMYK to RGB algorithm prince uses?

We don't convert CMYK to RGB at all, we embed the CMYK colors directly 
in the PDF file as-is. That is the only reason we bothered to add 
support for the cmyk() function: so that authors could specify 
exactly which CMYK color they wanted and have that carry through to the 
printed output (a customer requested this functionality).

[this must be done by PDF then can we find their algorithm? -- Nicholas]

> And what are acceptable parameters for the cmyk() function? Percentages 

We accept either four numbers between 0 and 1 or four percentages. We 
don't support mixing numbers and percentages, as the rgb() function does 
not support this.

I don't think that 0..255 makes sense for cmyk(), as there is no 
tradition of representing CMYK colors as a tuple of 8-bit values as far 
as I know, whereas there is for RGB colors.

Note that the CSS3 Color module is not entirely consistent in that HSL 
colors (which Prince does not support) specify the saturation and 
lightness components only with percentages, not numbers at all. However, 
RGBA colors specify the alpha value only as a number between 0 and 1, 
even though it would seem to make sense to also allow a percentage to 
specify the alpha.

[so it seems we should add percentage support but not 0-255, which resolves
that issue -- Nicholas]

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