RBG to CMYK conversion
Scott Hudziak
Red = 14Green = 68
Blue = 47
So, now, what is CMYK?
Cyan = ?
Magenta = ?
Yellow = ?
Black = ?
See what I mean?
hue
h...@pro-freedom.cts.com
ProLine: hue@pro-freedom
Internet: h...@pro-freedom.cts.com
UUCP: crash!pro-freedom!hue
r...@adeptsln.cts.com
> Does anyone know how to convert from RBG to CMYK? For example:
> Red = 14Green = 68
> Blue = 47
>
> So, now, what is CMYK?
> Cyan = ?
> Magenta = ?
> Yellow = ?
> Black = ?
>
> See what I mean?
Yes, you just asked a question on par with "what is the TRUE religion?"
There is no 'pat' answer for the RGB->CMYK conversion, as many other variables
figure in. UCR, GCR, process color purity (cyan ink has magenta & yellow,
magenta ink has cyan & yellow etc.), all contribute to the CMYK components.
Even the color of what the CMYK will be printed on, comes into play, somewhat.
(it's rumored that the phase of the moon is thrown in sometimes.) Anybody that
does RGB->CMYK conversions (also known as process separations) usually keeps
their algorithms as secret as the Coca-Cola formula. (Big money in digital
pre-press).
BUT.. All of this is to get 'accurate' or even 'usable' conversion.. If you
want just a rough guestimate (which you would RARELY if NEVER want), you can
use these simple formuli: (all values are in the range 0.0 to 1.0) All of this
is gleened from Photoshop's separation preferences.
rawC = 1.0 - R
rawM = 1.0 - G
rawY = 1.0 - B
minCMY = minimum(rawC,rawM,rawY)
C = rawC - minCMY * .55
M = rawM - minCMY * .55
Y = rawY - minCMY * .65
minCMY = minCMY * 2 - 1.0 // this should be an exponential..
// but this is an o.k. approx.
K = clipped_between(0.0,minCMY, 1.0)
Like I said, this is a ROUGH estimate.. DON'T TRY PRINTING WITH THESE!!!
(no flames required)
--
Roy Lovejoy | internet: r...@adeptsln.cts.com
Software Philosopher | AppleLink: adept
Adept Solutions | CIS: 72447,1447
.....................| dual certified developer: NeXT & Apple ;)