For example, as shown below, I want to liquefy Patrick into a thin man.

Carry out filtration liquefaction

Patrick has lost weight, but the surrounding background is also distorted, unless the picture with monochrome background can be directly liquefied, such as pure white, pure black and pure blue.

Cut: Cut off the layer you want to liquefy.

There are many kinds of matting tools. No matter which tool you use, its purpose is to dig out the target layer.

Then you can safely "slim down"

Then place a new background picture.

(ps: I'm really sorry, but the detailed process cannot be described in words here. If it is convenient, I can teach you remote operation in my spare time. If necessary, please click on my personal portrait and trust me privately. )