Photos today can be easily edited by means of resizing, cropping, adjusting the contrast, or changing an image’s format. As a result, new images are created that are similar to the original ones. Websites, web applications and mobile apps that allow user generated content uploads can benefit from identifying similar images.
If your site allows users to upload images, they can also upload various processed or manipulated versions of the same image. As described above, while the versions are not exactly identical, they are quite similar.