Question Get darkest color of a given texture

Anyone have any idea how to get the darkest/lightest point in 2d Texture? In shader graph.

I'm trying to use this for a Remap node. All I want to achieve is that my darkest color remaps to black, and my lightest color remaps to white.

While I can manually input the "min max" in the remap, I need it to be sourced from the texture, since I'll be using hundreds of different textures, each with different darkest/lightest points.

An alternative way of asking this is: how do I extract a grey scale gradient from a gray scale texture?