[metapost] defaultcolormodel

[Hans Hagen]

On 12-7-2011 4:37, Stephan Hennig wrote:
> schrieb luigi scarso:
>> On Mon, Jul 11, 2011 at 12:43 PM, Stephan Hennig<mailing_list at arcor.de>  wrote:
>>>
>>> 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)?
>>
>> There are several reasons:  one is  that "black colors are not all equals ":
>> http://en.wikipedia.org/wiki/Rich_black
>
> OK, thanks!  While I cannot see a difference between (0,0,0) and
> (0,0,0,1) in GSview, in Adobe Reader CMYK black is indeed greyish.  The
> attached code draws three shadings (from top to bottom):
>
>    * CMYK white to black,
>
>    * RGB black only,
>
>    * CMYK black (0,0,0,1) to 'registration black' (1,1,1,1).
>
> On my non-calibrated screen, the difference between RGB black and CMYK
> rich black disappears at a mix-in of around 30% colour components.

in acrobat you can change the way cmyk is handled by setting a different 
kind of target paper

keep in mind that when doing an rgb-cmyk-rgb conversion in a bitmap 
editor also some assumptions with respect to the medium can be enabled 
which is the reason why roundtrip won't work out as expected

Hans

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