How does ps slim down and the background is not deformed?
Filtration-Liquefaction: Using the liquefaction function, apply the frozen mask tool to the place where you don't want to deform, then this part will not move or deform. If you don't want to freeze, you can use the Freeze Mask tool. The next tool is called the Thawing Mask Tool. You can smear and thaw the frozen place just now.