No, you can't. But why do you need it to save it in there? if you want it to be store in the private area of your application (so your application is the only with access to it), you can do it, but if you want an image to be in your assets folder, you need to place it in there before you compile to create the apk.
Data Storage - Internal Memory
P.S. I don't recommend you to save large images on internal storage as this space is very limited in legacy devices.
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