information in images

Lang and I spent more time discussing how one measures the information in an image. It turns out that despite the fact that information is a quantitative property, how one calculates it depends on what parts of the data stream are expected to contain the information, and very different quantities are produced when you make different assumptions. For example, the information in an image, by the usual methods, does not change if you randomize the pixel order, even though most of us would say that the randomized picture contains much less information! That is because most methods for measuring the information consider only the pixel histogram, and not the pixel adjacency relations.

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