At the Web conference in Beijing last week, the Google researchers announced that they were working on a new technology, VisualRank, which is similar to PageRank, but aimed at images.
When we search images on the search engines, the only information that search engines can use to judge whether it is related or not is the image related text. The Google VisualRank aims to analyse the image content itself. If the new technology really works some day, the description contents for images would not be necessary any more. Search engines can find the most suitable images according to the images themself.