How does smoothing work near the borders between old and newly added images

[adamrouhiainen]

If you look closely when a masked region is inpainted, you can see that the original conditional pixels near the border have been edited slightly. I'm assuming this is to smooth out the border between the old and new images. What is specifically being used to edit the original image when the inpainted region is added? For example, is it a Gaussian blur, a cubic interpolation, etc.
Thank you