The scale invariance of natural images suggests an analogy to the statistical
mechanics of physical systems at a critical point. Here we examine the
distribution of pixels in small image patches and show how to construct the
corresponding thermodynamics. We find evidence for criticality in a diverging
specific heat, which corresponds to large fluctuations in how "surprising" we
find individual images, and in the quantitative form of the entropy vs. energy.
The energy landscape derived from our thermodynamic framework identifies
special image configurations that have intrinsic error correcting properties,
and neurons which could detect these features have a strong resemblance to the
cells found in primary visual cortex