Digital art is automatically copyrighted once it is created in a fixed or tangible form. You do not need to register for a copyright. In Hong Kong, there is in fact no copyright office for formal registration.
Copyright is time limited, and in Hong Kong how long copyright lasts depends on the format of the work, but in most cases it will last for 50 years after the death of the author/creator.
Disclaimer: Nothing in this website is intended to be nor should be constructed as legal advice. This is an educational project created by students. Please consult your lawyer for legal advice.