“…The importance of QPP has been widely recognized in text retrieval [3, 10-13, 18, 24-26, 35, 39, 40, 43, 44, 51, 54-56, 58, 63-65, 69, 76, 77], being an actively studied task nowadays [1, 2, 9, 14-16, 22, 32, 60]. However, in the context of content-based image retrieval (CBIR), the QPP task received comparably lower attention from the research community, with only a few studies addressing the topic [33,34,42,45,46,68,[70][71][72]74]. Furthermore, only a handful of papers [42,46,68,72] study query difficulty prediction in the queryby-example scenario, where the query is an image.…”