Concept-based image indexing, also variably named as “description-based” or “text-based” image indexing/retrieval, refers to retrieval from text-based indexing of images that may employ keywords, subject headings, captions, or natural language text (Chen & Rasmussen, 1999). It is opposed to Content-based image retrieval

Content-based image retrieval

Content-based image retrieval , also known as query by image content and content-based visual information retrieval is the application of computer vision techniques to the image retrieval problem, that is, the problem of searching for digital images in large databases....

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Chu (2001) confirms that there exist two distinctive research groups employing the content-based and description-based approaches, respectively. However, research in the content-based domain is currently dominating in the field, while the other approach has less visibility.