This is a bit of an abstract question, but bear with me. I am averaging images, to try and deduce what the average image of a specific subject looks like (just out of curiosity, it might produce some interesting results).
In order to know what kind of averaging method is permitted, i am trying to determine as what kind of data images can be classified (nominal, ordinal, interval or ratio). I would think a collection of images from a specific subject (creative commons portraits scraped from flickr for example) can be classified as nominal data, since there is no sense in ordering portraits (which would make it ordinal data, or higher).
In my opinion the images are on the same level as names, but instead of a linguistic representation of something, they are a visual representation of something (thereby functioning on the same level as a name). Which would make it nominal data.
But then again: digital images are in essence an array of numbers (rgb values), which could mean that it's measured at the ratio level (or at least the colors are). So a mean average is possible, but is it sensible?
My other question should clarify what it is i am trying to achieve: Averaging images