How to make raster friends with JS or PHP?

Question

PHP

(I ask you in advance not to answer the question if you do not understand it, it is better to ask again in the comments please)
Hello, an idea appeared in my head to implement an interesting task.
In order.
1. Task.
We have hundreds of images, for example motorcycles. It is necessary that some objects in the photo can be recognized, or at least get coordinates in px from the edge of the picture. For example, a wheel, next to the wheel, display a caption that this is a wheel. And all this in all the photos.
2. Idea
Use some kind of graphic tag like QR code, manually embed it in the image, or use a unique pixel of a certain and unique color, also I will find a way to put it on the images in a convenient way. and make sure that the pixel with this color is the only one.
Why be so sophisticated? This is interesting, I could just make a unique layout for each case, but I would like something like this so that this method can migrate somewhere else. This gives rise to many interesting questions, one of which I have shared with you.
I'm wondering if any of you have faced such a task, have you seen something similar somewhere?
Are there any libraries (maybe in php or js) or other ways of similar photo processing?