Re: RGBColor [?,?,?]

• To: mathgroup at smc.vnet.net
• Subject: [mg30884] Re: [mg30852] RGBColor [?,?,?]
• From: steffenz at server2.fo.fh-koeln.de
• Date: Sun, 23 Sep 2001 02:16:24 -0400 (EDT)
• Sender: owner-wri-mathgroup at wolfram.com

```Hi Eugene,

there are some mistakes right in the beginning of  Your problem.

> Date:          Thu, 20 Sep 2001 03:52:00 -0400 (EDT)
> From:          "eugene777" <eugene777 at freemail.absa.co.za>
To: mathgroup at smc.vnet.net
> To:            mathgroup at smc.vnet.net
> Subject: [mg30884]       [mg30852] RGBColor [?,?,?]

> Hello,
> Imagine Leonardo Da Vinci in mixing paints (colors), but he has only
> Mathematica for this reason.
> He knows yellow mixed with blue forms green and denotes:
> RGBColor[1,1,0] + RGBColor[0,0,1] = RGBColor[0,1,0]

Yellow and blue is not green, but white!

RGB means additive color mixing (mixing of colored light like
a monitor)
RGBColor[1,1,0] + RGBColor[0,0,1] = RGBColor[1,1,1]

What You want to do is subtractive color mixing. This is based on
yellow, magenta and cyan YMC (like an inkjet)

Yellow mixed with cyan forms green,
magenta mixed with yellow forms red,
cyan mixed with magenta forms blue.

> He knows red mixed with yellow forms orange and denotes:
> RGBColor[1,0,0] + RGBColor[1,1,0] = RGBColor[1,.5,0]
> ... and generally he denotes:
> RGBColor[r1,g1,b1] + RGBColor[r2,g2,b2] = RGBColor[r3,g3,b3]
>

Here is RGB working {r3,g3,b3}=({r1,g1,b1}+{r2,g2,b2})/2.
in YMC: YMC[1,1,0](red) + YMC[1,0,0](yellow) = YMC[1,.5,0](orange)

YMC[1,0,0](yellow) + YMC[0,1,1](blue) = YMC[1,1,1](black!!!)
This is not what everybody would expect, because what You find in
most color boxes is not a pure blue but cyan:
YMC[1,0,0](yellow) + YMC[0,0,1](cyan) = YMC[1,0,1](green)

> Now he needs to put a detail on the picture colored RGBColor[.375,.988,.164]
> but he does not know which colors to mix. So he needs an algorithm. He wants
> to know and the opposite û mixing any two or more colors what will be the
> resulting color.
> * Question1*:
> RGBColor[r1,g1,b1] + RGBColor[r2,g2,b2] = RGBColor[?,?,?]
> ** Question2 **:
> RGBColor[r3,g3,b3] = RGBColor[?,?,?] + RGBColor[?,?,?]
>
> *******************************************************
> Two overlapped disks result three sectors: {1,2,12}.
> Three overlapped disks result maximum seven sectors {1,2,3,12,13,23,123}.
> *** Question3 ***(graphical) :
> I ask you how could I plot few randomly overlapped figures (say disks) to
> display these overlapped sectors with there resulting (mixed) color?
>
> Thank you in advance for any help.
> Eugene
>

I don´t know if a YMC[] function is defined but I think there will be
something like this.

Steffen

Dipl.-Ing. Steffen Zozgornik

Institut für Licht- und Bautechnik
an der Fachhochschule Köln
Lustheide 85
D - 51 427 Bergisch Gladbach

Tel.: +49 - 2204 - 30 14 - 15
Fax:  +49 - 2204 - 30 14 - 58

```

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