Gradient Map Filter : for images and bitmap textures

Ideas
1

This could be a nice filter.

Reference:

2

That would be great but unfortunately i cant find any implementation of that filter around, its probably PS specific (and proprietary)

3

I did a bit of research under "duotone effect" and found this. There's a play store link in the post.

https://dribbble.com/shots/3251564-Duotone-Effect-app-interface

4

Could you tell me how you did that in PS?