[rayiner]

It's a bad analogy. Binary and hex are just different formats for representing the same number. Spatial domain and frequency domain are different views of a complex data set. In the spatial domain, you are looking at the intensity of different points of the image. In the frequency domain, you are looking at the frequencies of intensity changes in patterns in the image.

A good way to develop an intuition for the fourier space is to look at simple images and their DFT transforms: http://web.cs.wpi.edu/~emmanuel/courses/cs545/S14/slides/lec... (3/4 of the way through the slide deck).

This analysis of a "bell pepper" image and its transform is also helpful: https://books.google.com/books?id=6TOUgytafmQC&pg=PA116&lpg=....

As for why you want to do this: throwing away bits in the spatial domain eliminates distinctions between similar intensities, making things look blocky. In the frequency domain, however, you can throw away high-frequency information, which tends to soften patterns like the speaker grills in the MBP image that the human eye isn't that sensitive to to begin with.

[astrange]

> Spatial domain and frequency domain are different views of a complex data set.

Or in this case, a real data set.