How to compare images?

Question

PHP

There are certain VKontakte groups, many of a thousand or two groups. There are images in these groups, I think that in all groups of the desired subject there are several million images. I need to upload them and find the same ones among them (that is, the image is the same, just posted in different groups), preferably including those that have been resized by resizing and applying an inscription / watermark. Identical images are grouped into one and the likes for all copies of the image are counted, the likes are summed up and this sum is the rating of the conditional "combined" photo-image.
Can you tell me the best way to approach this issue? First of all, I'm talking about comparing photos in such volumes and about comparing resized images (inscription, watermark, resizing). Thank you.

Answer 1

php.net/manual/en/imagick.compareimages.php