1. Introduction
Digital artwork spans a broad range of content depicted in diverse visual styles. Learning a representation suitable for searching artwork based on visual style is an open challenge, particularly when discriminating between subtle, fine-grained [39], [37], [25] variations in style. This is due to the difficulties of both (i) defining a suitable fine-grained ontology to label styles and (ii) the expert annotation task. Research to date has therefore focused upon coarse-grain discrimination of a limited number of styles [17], [6].