It is very easy to connect to Google Images, write the name of what you are looking for and then have several images available for that subject. For thereverse operation, or starting fromimage find a first name or very similar matches in terms of others images, we can rely on several online services.
The purposes can be different; snoop to find photos of someone, to discover if they reused images we created, find the identity of a person we only have a photo of or search for wallpapers similar to our favorite wallpaper.
I propose you 3 among the best services that make this "reverse lookup".
1. www.TinEye.com one of the best services for the identification algorithm it uses; It is possible to find the real source of an image, like it is used on the web, which ones sites they host it and if there are versions of the same image / photo at a higher one resolution or with colors different. The team that created the service also periodically provides information on the latest updates to the index of the images they manage. It is possible to do theupload of an'image that we have on the computer or directly enter theurl that points to that image.
In the list of similar images, there are also the percentages which indicate how "close" the image is from the original photo. Obviously the first images will be absolutely identifying, going in the last results, we will also have photos of very similar people.