• Visual properties, capturing the setting of an image such as landscape, cityscape, seascape;

 

• Text, looking for any textual cue within the visual content for better identification;

 

• Human faces whose detection may be performed automatically in a reliable fashion and which form a efficient cue for classification; • object detector (such as «car detector») may be finally designed and finetuned in a very generic setting.

 

However, the more one gets specific, the less robust to errors the characterization will be. Despite this criticism, automated image analysis has led to unquestionable success. The performance of image compression systems such as the JPEG standard allowing efficient Web image transfers relies on a shallow understanding of the content. Further, as mentioned, faces and text are items that may be handled well by automated systems. In our GIFT system [GIFT], the image may interactively be searched by

visual content based on color and texture. By successively marking negative and positive examples, the search is refined and characteristics are filtered so as to match an underlying semantic concept.

While the system is achieving its aim of retrieving images of a given class, a careful study of the results shows that, even towards the end of the search, our GIFT system is not actually able to express the underlying semantic concepts. That is, it is still confused with unrelated visual examples. This would clearly not be the case using a text-based system but then would require a complete and exhaustive annotation of the visual content that is know to be unpractical and that we try to avoid here. Summarizing, if we take the case of art, we may easily characterize e.g. a given painting by its color and associated layout so that we would be able to distinguish copies of that specific painting with a collection of images. This would be useful to track unlawful appearances of images of that painting on the Web for example. [2] At the other end of the scale, we also may characterize a school of painters by the color and strokes they use. Impressionism is easily characterized in this way. This