An interesting site has recently opened:
tineye.com , which
Mitesha had already
written about , but then it was in the stage of closed testing.

In a nutshell, the principle of operation is as follows: the site searches for images, but not by keywords, but by the original image by the uploaded user.
')
For example:
original picture
found
Part of the FAQ from the official site:
What makes TinEye?
TinEye does for images what Google does for text.
Just as you enter text into Google to find web pages containing this text using TinEye, you upload a picture to find pages with this image (and modified versions).
How it works?
TinEye uses advanced pattern recognition algorithms to find images on the Internet without using metadata or watermarks.
TinEye instantly analyzes the original image to create a compact digital signature or “fingerprint” for it. TinEye searches your image online by comparing its fingerprints with other TinEye-indexed images.
How many images in the search index have TinEye?
To date, TinEye has indexed 701,666,310 images from the Internet. TinEye scans new images from the network constantly, so this number is increasing.
Can I use images that I find through TinEye for free?
Any image found by the TinEye search engine may be copyrighted. Although TinEye allows you to find and view images using our service, we cannot grant you permission to use them for purposes other than browsing the Internet. If you want to use any images found by our service, we strongly recommend that you contact the image owner.