Image rotation with and without linear interpolation, how to explain these changes?

Question

Graphic arts

Hello everyone, how can I best explain this behavior in the following operations:
1) the original image

2) Rotated the image 45 degrees and returned it to -45 degrees Interpolation: None

3) Rotated the image 45 degrees and returned it to -45 degrees Interpolation: Linear

- As for linear interpolation, black and white values ​​are mixed there because of the algorithm that takes the average value, and this is such a light-dark gray mess, right?
- But what is the best way to explain the changes from example "2", without interpolation?

Answer 1

Well, how about without interpolation ? And garbage because of the chaotic choice of reference points due to irrational coefficients of linear transformation (specifically, rotation).