Yes, though there is confusion in the second paragraph of that reply about what it means for the image to be a "matrix". It's being a matrix has no bearing on

Yes, though there is confusion in the second paragraph of that reply about what it means for the image to be a "matrix". It's being a matrix has no bearing on converting it to grayscale or sepia. It may as well be an unordered bag of pixels as far as those operations are concerned. I think most beginners would come away with the wrong impression that linear algebra or fourier transforms were important for these basic operations when one or two for loops is quite enough. When I teach this material, that's where I begin and it is very effective. Also they use the term contrast incorrectly. They're describing a low pass filter (blur) in the example but refer to contrast -- that post would lead beginners very astray.