Un-mix (or remove) a color?

[drawtheliner]

Although not possible in real life, can I simulate removing one color from another using mixbox?

For example, since blue and yellow make green, removing yellow from green should make blue.

I tried using a negative mixing ratio and that didn't seem to work.
I also tried inverting the color to be removed first (so a color like (0,5,255) becomes (255,250,0)), but I'm not sure if it worked.

[knokelmaat]

Mixing is just a linear operation in the latent space (once RGB is converted to latent representation). So inverting that operation is very straightforward (python):

#!/usr/bin/python

import mixbox
import tkinter

color1_rgb = (167, 41, 32)
color1_latent = mixbox.rgb_to_latent(color1_rgb)
color2_rgb = (0, 181, 26)
color2_latent = mixbox.rgb_to_latent(color2_rgb)

# Mix 0.2 of color1 with 0.8 of color2
color_mix_latent = [0.2 * color1_latent[i] + 0.8 * color2_latent[i] for i in range(mixbox.LATENT_SIZE)]
color_mix_rgb = mixbox.latent_to_rgb(color_mix_latent)

# Convert mixed color back from RGB -> LATENT
#color_mix_latent = mixbox.rgb_to_latent(color_mix_rgb)

# Unmix
color1_guess_latent = [(color_mix_latent[i] - 0.8 * color2_latent[i]) / 0.2 for i in range(mixbox.LATENT_SIZE)]
color1_guess_rgb = mixbox.latent_to_rgb(color1_guess_latent)

# Print results
print("0.2 of", color1_rgb, "and 0.8 of", color2_rgb, "->", color_mix_rgb)
print("take 0.8 of ", color2_rgb, "out of", color_mix_rgb, "->", color1_guess_rgb)

# Show results graphically
root = tkinter.Tk()

e = tkinter.Label(root, width=20,height=2,text='#%02x%02x%02x' % color1_rgb, background='#%02x%02x%02x' % color1_rgb)
e.grid(row=0)
e = tkinter.Label(root, width=20,height=2,text='#%02x%02x%02x' % color2_rgb, background='#%02x%02x%02x' % color2_rgb)
e.grid(row=1)
e = tkinter.Label(root, width=20,height=2,text='#%02x%02x%02x' % color_mix_rgb, background='#%02x%02x%02x' % color_mix_rgb)
e.grid(row=2)
e = tkinter.Label(root, width=20,height=2,text='#%02x%02x%02x' % color1_guess_rgb, background='#%02x%02x%02x' % color1_guess_rgb)
e.grid(row=3)

root.mainloop()

Running this results in a color1_guess_rgb that is identical to the original color1.

However, if you look closely, you can see that I commented out the conversion from LATENT -> RGB -> LATENT for the mixed color. If I leave that line in, you no longer get a similar result. This is because seemingly LATENT -> RGB -> LATENT does not give similar results in latent space. But I suppose this is an altogether different issue that can be discussed (and is probably linked to #11).

[drawtheliner]

Thank you for that!