TinEye Labs – “TinEye is a reverse image search engine. Search by image: Give it an image and it will tell you where the image appears on the web. Try TinEye’s image recognition and search capabilities. Our image search products are available for licensing and can be used to search your image collections.
Multicolr: search images by color – We used MulticolorEngine to make 20 million Creative Commons images on Flickr searchable by color. Search for photos by up to 5 different colors at once—give it a try!
Color Extraction – extract color values with MulticolorEngine – Create a color palette from any image with MulticolorEngine. This demonstration identifies the top 10 colors in your image, and even finds the closest color name! Works with JPGs, PNGs, and GIFs.”