Disclaimer: Ask a lawyer, we are designers.
As mentioned in the comments, if you just recreate the outlines or shapes, and the result looks exactly or very similar to the original piece, you would be infringing copyright because of substantial similarity.
To win a claim of copyright infringement in civil or criminal court [US], a
plaintiff must show he or she owns a valid copyright, the defendant
actually copied the work, and the level of copying amounts to
misappropriation. Under the doctrine of substantial similarity,
a work can be found to infringe copyright even if the wording of text
has been changed or visual or audible elements are altered.
Explain to your client what he/she is asking is illegal (and very unethical, by itself and because you are a designer as well). Check this question, you'll find some good ways to deal with this situation: