Creating a custom shape gradient

Hey. I'm trying to vectorize images of guitars for my own practice. I'm trying to find a way to create the gradient I want the guitar to be colored with to be in the shape of the guitar (see attached screenshot). but there are only linear and radial gradient. Can I do something like this? Or maybe there is a different way to do this? Thanks in advance.

you can see here the guitar is painted in a gradient like color. how can i make my gradient fill the shape of the guitar like this?