Currently, ui.Image.dispose tries to clear the Dart wrapper, but does not release the underlying Skia resources until a GC is performed. It should be possible to do this more efficiently/quickly. See more discussion at #56482

A dispose method on a Dart object that allocates significant native resources should at least make an effort to dispose them. One challenge I'm seeing with this is that something else might still be referrring to the underlying SkImage, and I'm still trying to track down what that is or if we can do anything about it.

/cc @jason-simmons @chinmaygarde