Where can i find a search engine that searches by image rather then by words?

Maybe Riya.com is the answer closest to your question. Riya is a photo search engine using face recognition & text recognition technology in images. There are algorithms being made on the same question, but still none has come out 100% efficient. A search engine that searches by image rather than words will defintely have a lot of pressure upon it, as comparing pictures is a hellotta tough than comparing words. You input an image and the chances of another similar to it will be varying highly, depending upon the accuracy level we need it to be. Take into consideration... the image size, color, type, even the dust, aberrations, imperfections in the image'll count here. No small deal we are talking here. Need extreme processing and subtle calculations