Source: family firm is in the paint industry, worked in it for close to fifteen years.
If it somehow works I’ll avoid having to paint the whole house.
I've been quite surprised by how non-uniform most digital camera imagers and in-body post processing color pipelines muck with the spectrum coming off the sensor, all in the name of producing a more pleasing JPEG. If you still want to do what you described, I'd use RAW and use dcraw to convert to tiff, and open that in gimp.
Take your samples to a good paint store. Those machines are more sophisticated then you may think.
The white point (color temperature) is easy, using whatever light source they're being illuminated with.
But what determines whether a particular white is (240, 240, 240) or (250, 250, 250) or (255, 255, 255)? The exposure seems far more arbitrary. Is there some kind of maximally bright matte "reference white" material photographed next to each swatch, that then gets calibrated to (255, 255, 255) or similar?
If so, it would be pretty cool if you could buy a reference white chip like that, hold it up to a painted wall in your house, and have an app that could take a photo with both and output the "true" current paint color.
You're right to wonder about "what is white" which gets into topics of 'chromatic adaptation', 'color constancy', and 'discounting the illuminant'.
If you get a perfectly diffuse white tile, what color is it when illuminant by incandescent versus fluorescent? And there are more than a few CIE F illuminants, and more proprietary ones. And hence each application tends to standardize on, and thus assume, an illuminant. You can use some other illuminant if you want, but then you're in custom territory and it wouldn't surprise me if some companies are doing that, secret sauce.
In special cases like automotive and textiles, it's common to see multiple spectral values due to different colors at different angles, and thus spectrogoniometry.
However color matching is more complex than that. "Color of the light source" varies considerably, not only due to the illuminant itself, but also the materials the illuminant is reflecting off of (e.g. walls). And color temperature only defines black bodies, which most light sources are not: you need information about the full spectrum of the illuminant to determine how it interacts with the material to be color-matched. This is getting a bit into metamerism: https://en.wikipedia.org/wiki/Metamerism_(color) (Of course, paint cannot match an arbitrary spectrum. Matching under specific lighting conditions is the least you can hope for.)
And the above is considering color of a surface only as a scalar value, but it's really a function of illumination angle as well, due to gloss. Direct lighting on a glossy surface reflects more of the color of the gloss, whereas oblique lighting reflects than the paint itself. Diffuse lighting is some combination thereof.
(I am not a color scientist by any means, just interested in the topic. Experts please correct!)
https://en.wikipedia.org/wiki/Middle_gray
Fascinating. I never knew there was an "standard" mapping between real-world colors and RGB.
Now if only online clothing store photos would map to that, so that the olive green coat I order doesn't turn out to be closer to medium brown or vice-versa... :P
What are these? The website doesn't seem to explain anywhere.
That way the app could adjust for fading and tell me what color that paint was originally.
e.g. https://www.matchmypaintcolor.com/ppg/medieval-forest shows RGB 1,116,120 for all 3 swatches, but only the Maxi Teal is that RGB, the other tiles have other RGB values.
Edit: actually it’s almost possible to do what I need. It’s just be much easier if it was possible to find closest match. Still this could be helpful.
Compare the pair:
- https://www.matchmypaintcolor.com/ (this site)
- http://surfweb.com/ (fake site)
Any intentions on adding suggested palettes?
Any idea how this process compares?
