Mixing paints (!!Con 2016)
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Mixing Paint! With Computers!
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Transcript of Mixing paints (!!Con 2016)
Mixing Paint!With Computers!
Let’s talk about colors
Let’s talk about colors
Let’s talk about colors
Colors in Code
Colors as combination of Red, green, blue lights
RGB Model
Mixing Colors
Mixing Colors
Mixing Colors
Mixing Colors
Mixing Colors
Mixing Colors
Mixing Colors
R: 1.0G: 0B: 0
R: 1.0G: 1.0B: 0
R: 1.0G: 0.5B: 0
Mixing Colors?
R: 0G: 0
B: 1.0
R: 0.5G: 0.5B: 0.5
R: 1.0G: 1.0B: 0
So how does mixing paint work?
• Let’s talk about physics
Visible Light Spectrum
380 nm 750 nm
Subtractive color
CMYK color model
Mixing Colors Again
C: 1.0M: 1.0
Y: 0
C: 0M: 0
Y: 1.0
C: 1.0M: 1.0Y: 1.0
Now what?
• Other color spaces?• Need to convert to RGB to display on screen
Let’s try physics
Kubelka-Munk theory
• Returns reflectance of light for a layer of pigment on a surface
Kubelka-Munk theory
White light
Kubelka-Munk theory
White light
Scattering,Absorption,Etc.
Kubelka-Munk theory
White light
Scattering,Absorption,Etc. Colored light
Kubelka-Munk theory
Case Study: Krita Color Blending
Case Study: Krita Color Blending
Removed in 2012 :<
Kubelka-Munk theory
• It’s complicated to implement.• Needs information not provided by RGB• Physically accurate (to a point)• Can we do better?
Case Study: Paper (iPad App)
Summary
• Mixing colors is complicated• Color representation in computers not optimized for blending colors• You can use physics!• Or do it all manually• To get realistic (or not realistic) color blending
Thank you!
Diana Liao@dmliao
Extras
• Stuff that didn’t make it into the 10 minutes, and other links
CMYK?
• So the CMY part stands for Cyan, Magenta, and Yellow• K = Key (Black)• Avoids using up all your colored inks when printing B&W
Color is not intuitive
Kubelka-Munk theory
(1–R)²/2R = k/s = Ac/s
Where:R = reflectancek = absorption coefficients = scattering coefficientc = concentration of the absorbing speciesA = absorbance
Solve for R and convert reflectance to RGB
References
• http://vis.computer.org/vis2004/DVD/infovis/papers/gossett.pdf - a paper for using different color spaces to mix colors, which I didn’t have time to go over• https://www.youtube.com/watch?v=lyLPZDVdQiQ – video for Krita’s
paint mixer• http://
www.fastcompany.com/3002676/open-company/magical-tech-behind-paper-ipads-color-mixing-perfection - article on Paper’s color mixer
References cont’d
• http://www.ftir.ru/docs/%D0%A1%D0%BF%D1%80%D0%B0%D0%B2%D0%BE%D1%87%D0%BD%D1%8B%D0%B5%20%D0%BC%D0%B0%D1%82%D0%B5%D1%80%D0%B8%D0%B0%D0%BB%D1%8B/drift%20theory.pdf – a PDF that comes pretty close to explaining what it is (and its most often used form in programs)• http://www.rpdms.com/wineyrpt.html• https://quickgit.kde.org/?
p=krita.git&a=tree&h=7a7bac0a9ff5767e59ef856fb3fa9b96865b8eb8&hb=202e453cbae6417748bca3d93588e0ad4ae1e7c5&f=krita%2Fplugins%2Fextensions%2Fpainterlyframework – Krita’s Kubelka-Munk based color mixer, from a commit back when it was still part of the project
Aka me trying to google the Kubelka-Munk theory
