[metapost] defaultcolormodel

Stephan Hennig mailing_list at arcor.de
Tue Jul 12 16:37:15 CEST 2011

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.

Best regards,
Stephan Hennig

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