Replace the part you paint over with something new, and leave the rest alone.
The area you mask is cleared away before the model starts. The model is then asked what belongs there, given the prompt and everything around the hole.That clearing is the whole difference from , and it has one consequence worth knowing in advance: there is no strength slider here. The panel sends the maximum and does not offer you the slider. A lower value does not soften the edit; it leaves the area unfinished. The examples show it: at a middling strength the masked area comes back as a flat grey patch in the shape of the brush, because there was nothing left to work from and not enough of the pass left to invent anything.Use it when what is there should go. Use the masked kind of image-to-image when what is there should change.Fewer workers serve this than serve an ordinary request, so expect to wait a little longer. It also needs a Stable Diffusion 1.5, 2 or XL model, and it cannot be combined with .To make the picture larger by painting new ground around it, see .