How to find out the translucency level in png?

Question

Images

There is a picture . The walls are translucent.
Is it possible somehow in Photoshop or other editor to find out how transparent they are (say, as a percentage)?

Answer 1

I came up with the following:
1. Click on the layer icon with Ctrl pressed to create a selection on the layer's alpha
2. Create a layer mask by clicking the appropriate button at the bottom of the layers window.
3. Switch to the mask (Alt+click on the mask)
4. Move the picker and see the K value in the Info window.
Only in my opinion this is a crutch, I thought Photoshop works more conveniently with alpha.
I would be glad if someone tells me how to do it right.