Is `scikit-image` really needed as a direct dependency?

I noticed that `scikit-image` is listed as a required dependency, but I couldn’t find any direct imports of it in the `rembg` codebase.

Is it actually used by `rembg`, or only pulled in via other libraries (e.g., `pymatting`)?
If it’s not directly needed, would it make sense to drop it or move it to optional extras to reduce install size?

Thanks!
