Returns the default colour spaces of a resource dictionary.
public PdfDefaultColorSpaces GetDefaultColorSpaces(CosDictionary? resources)
The resource dictionary, such as Resources; null for none.
ISO 32000-2 §8.6.5.6. Invalid defaults are ignored with a diagnostic. Read again after the dictionary's ColorSpace
subdictionary changes or an object is added or removed (which can change what a reference in it resolves to, §7.3.10).