How to upload photos to the wall and generate a "mosaic" on the wall from them?

Question

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Good afternoon, who knows the algorithm for uploading photos to the wall and generating a "mosaic" from photos on the wall in vk.com?
The information is necessary for writing a clear task for programmers, so as not to explain on the fingers.

Answer 1

For the mosaic, nothing special needs to be done. Just load and attach the pictures to the post on the wall and that's it. VK will make the mosaic itself)
The process of uploading photos is written in the documentation .
However, the documentation is not so transparent. There, in some places you need to think specifically in order to understand what actually needs to be done. Here is an example of my implementation of uploading a photo and posting to a wall.