-1
$\begingroup$

Typically a gray-scale image gives us more information about an image in terms of a signal processing problem. But when does a color channel carry more info than a gray-scale channel?

I understand the use of FFT applied to gray-scale channels for this usual phenomena, but I want to know what is an instance of the opposite being true.

$\endgroup$
  • $\begingroup$ Let's say you generate a greyscale image from an RGB by defining it as average of the three color channels: $Y= \frac13(R + G+B)$. Now, lets have an image where the green channel always decreases in intensity when the red channel gains intensity (for example: picture of cherries getting ripe. They're either green or red.) Then, the sum will contain less information on the ripeness than the red channel alone. I found that example easy to come up with. Can you find another one? $\endgroup$ – Marcus Müller Dec 2 '18 at 9:57
  • $\begingroup$ RGB has three color channels. Do you mean just one of them (R, G, or B)? $\endgroup$ – Olli Niemitalo Dec 2 '18 at 17:05
1
$\begingroup$

Define a greyscale picture as linear combination of its color channels¹.

Then your greyscale picture's entropy inherently is lower than a single color channel's entropy if there's an overall negative correlation between that single channel and the linear combination of the others. Entropy is the expectation of information.

I understand the use of FFT applied to gray-scale channels for this usual phenomena, but I want to know what is an instance of the opposite being true.

The FFT doesn't have anything to do with this – it just transforms channels isolatedly from a spatial base to a spatial frequency base.


¹ not all color models work like that. We can still work with that and declare the nonlinearity an error...

$\endgroup$

Your Answer

By clicking "Post Your Answer", you acknowledge that you have read our updated terms of service, privacy policy and cookie policy, and that your continued use of the website is subject to these policies.

Not the answer you're looking for? Browse other questions tagged or ask your own question.