It may be tricky to use that routine on a spectral library since it was designed for use with an image. If you reform the library so it looks like an image it may work. Or you can just open your spectral library and view all the spectra, then use the Continuum Removal Plot function and save it to a new spectral library.

Thank you for the advice. It wasn't necessary to change it to an image structure at last. Finally I found out it's needed to have 2 lines in a spectral library at least. So I modified spectral libraries in this way.. .