Just use image processing software to process it. Adobe Photoshop (commonly known as PS) is the most widely used and powerful. If you can't use it, you can search for some tutorials, which is almost enough.

In addition, there are many softwares available, such as light and shadow magicians and cows, which are relatively easy to operate.

Which one you sent seems to have changed the size of the picture below, and made a reverse angle effect with the shadow of the picture. Type a few words on the picture to set the font effect.

I made a Luffy set myself, which belongs to PS. The technology is not good, but you can do whatever you want if you understand it. Sign in my space:/sign521/album/%ba% a3% D4% F4% CD% F5% C7% A9% C3% FB% b5% b5.