Real composition concerns constituents that form a concrete entity; a human body made of organs is a basic illustration. Comparing a complex entity with another does not automatically make the point of comparison composite.
Constructed or conceptual composition is a unified aspect abstracted by the mind from several things. White points scattered against darkness are distinct things but can form one visual pattern for a comparison.
Therefore composition of the terms must be distinguished from composition of the point of resemblance. Complex objects may share a simple quality, while simple objects may be compared through an elaborate configuration of features.