How to blend/mix two colors like real paint?

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Hey Codeproject,

I'm wondering how you blend two colors like you would with paint in real life. For instance, blending red and blue would result in purple. I'm wondering this because I'd also like the opacity of the color to play in as a component (meaning that if the alpha is 255 it would blend harder than it if it wouldn't.)

To clarify, [Here's] a picture of what I want to be able to do.

C#

public Color PaintBlendColors(Color One, Color Two)
{
   Color Col;
   /*Col = Blend?*/
   return Col;
}

Best Regards,
- Edz

What I have tried:

I've so far tried using a pre-build function in Monogame/XNA called Color.Lerp, but this does not give the desired effect.

Posted 13-Aug-16 1:37am

Member 11841791

Updated 2-Dec-20 11:53am

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Patrice T · Answer 1 · 2016-08-13T01:58:00

Solution 1

You can try to calc the mean of the 2 colors

C#

Col.Red= (One.Red+ Two.Red)/ 2;
...

Posted 13-Aug-16 1:58am

Patrice T

Comments

Member 11841791 13-Aug-16 8:06am

Combining red and yellow to get orange doesn't work that way. :/

[no name] 13-Aug-16 8:07am

No, sorry, that has absolut nothing to do with simulating Color mixing of paints. Compare mixing paints Subtractive color - Wikipedia, the free encyclopedia[^] and mixing RGB Color for e.g. a Screen Additive color - Wikipedia, the free encyclopedia[^].
The answer would deserves a 1, I do _not_ vote...

Member 11841791 13-Aug-16 8:13am

Woah, means of mixing seems to have fancy names. Thanks for clarifying!

Member 11841791 13-Aug-16 8:17am

Also this is what the .Lerp function does. It basically moves one color to another color with a given value. (0.5f) in your example.

[no name] 13-Aug-16 8:18am

I didn't make an example :-)

Member 11841791 13-Aug-16 8:20am

No, haha, I meant the guy who wrote the answer.

Member 11841791 13-Aug-16 8:36am

Oh cool, I finally found something at page 5,000 in Google. http://stackoverflow.com/questions/1351442/is-there-an-algorithm-for-color-mixing-that-works-like-mixing-real-colors

NewColor.R = (Color1.R * Color2.R)/255
NewColor.G = (Color1.G * Color2.G)/255
NewColor.B = (Color1.B * Color2.B)/255

I'll give it a shot and see what I can come up with.

My current function.

public static Color MixColorsSubtractive(Color A, Color B)
{
return new Color(A.R * B.R / 255, A.G * B.G / 255, A.B * B.B / 255, (1f / (255 * 255)) * A.A * B.A);
}

[no name] 13-Aug-16 8:56am

Concerning Stackoverflow Link: I did not read it carefully, so I can't judge. But with this (Quote):
"The correct answer is NO, because there is no correct working model of how "color mixing in the real world" really works. It is FAR too complex and conditional and not really at all like the simple Red-Blue-Yellow stuff that we learned in school (it in fact requires all of Chemistry and a lot of Physics and Biology to resolve)."
I do not agree, at least not at the Moment.

I will think about your question and try to answer, but it Needs some time ;)

N.B: I do not exactly understand where you see a Problem with Alpha blend... any more Information from your side?

Member 11841791 13-Aug-16 8:59am

Oh, there's not really an existing issue. I just assume that in the real world that the "more transparent" your color is, the more transparent the resulting mix would be. I'm not a real painter though, so don't ask me. I'll first try without the whole "alpha" or deal.

Also I agree with you. It isn't that complex, and as a great guy always said; there's math in everything. Thought alpha is not really a paint term, because alpha in the real world would be light - which is not subtractive blending.

I'm also done fixing all the existing bugs in my app, and then I'll find out how good it works.

Member 11841791 13-Aug-16 9:29am

Okay, so I just realized what I meant with alpha. (Sorry when I'm programming my English or language skills as a whole just drop down to 20%.) The alpha I mentioned earlier was suppose to be when it comes to water paint, but for now I'd be happy to just have the regular paint working out.

The code I gave you has a problem, and the problem is that when it comes to full colors for instance: (255, 0, 0) (Red) and (0, 0, 255) (Blue) it's suppose to make purple.

However, since these values are 0, when it does Red.R * Blue.R it will return 0, and thus black. I think there's an ugly way to fix it by making the minimum 1, in either case this does not work properly.

Patrice T 13-Aug-16 13:55pm

I guess it could make a Solution