[metapost] defaultcolormodel

luigi scarso luigi.scarso at gmail.com
Mon Jul 11 12:52:37 CEST 2011

On Mon, Jul 11, 2011 at 12:43 PM, Stephan Hennig <mailing_list at arcor.de> wrote:
> schrieb luigi scarso:
>> Conversion between color spaces needs a color profile.
>> For example (0,0,0) -> (0,0,0,1) not always is the best choice.
>> Generally a rgb color space is the a good choice:
>> practically many  monitors and cameras (hence jpeg) have the same
>> gamut (ie, the same color profile)
>> and it is  one of the wider color space also --- i.e. one can assume
>> that a rgb color is a real color
>> A cmyk is often a virtual color: you need the profile of the medium
>> (usually the paper) .
>> And the profiles *differ* each other.
> General colour space conversion requires profiles, true.  But speaking
> about black only, what could be wrong with a mapping (0,0,0) <==> (0,0,0,1)?
> Especially, if your looking at RGB colours as true colours that don't
> require a profile for interpretation.  Then (0,0,0) must be interpreted
> as pure black.  What would be a better match to pure black than
> (0,0,0,1) in print?
> Best regards,
> Stephan Hennig

There are several reasons:  one is  that "black colors are not all equals ":

Remember that theoretically cmy = (1,1,1) -(rgb)
The k component hence is added for some practical reasons,
for example

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