I came across this "texture analysis" technique in a paper called "Identifying structural complexity in aeromagnetic data: An image analysis approach to greenfields gold exploration" by E. Holden et al. and I couldn't really find the meaning of whatever this is anywhere.
context: "In this paper, we detect edges (i.e., magnetic discontinuities) by firstly enhancing local magnetic variations using texture analysis and then finding ridges within the texture analysis outputs using a contrast-invariant line detection technique. Finally, the texture ridges are identified and vectorised."
A contrast-invariant function is one that yields the same output before or after scaling intensities (i.e. increasing or decreasing contrast), or that yields the same output if the scaling is applied before or after applying the function. For example, the function $g$ is contrast invariant if
$$g(f) = g(Cf)\;,\qquad \text{or} \qquad Cg(f) = g(Cf)\;,$$
given an image $f$ and a positive constant $C$ (some contrast-invariant line detection algorithms might also yield the same results if $C$ is negative, but obviously not if it is zero).