How to make multiple pictures for the announcement automatically?

Question

1C-Bitrix

I am new to 1C-Bitrix. There are several pictures for the products. Detailed pictures should be large (it is possible to expand them), and for the announcement - the same, but reduced.
From a detailed picture, you can automatically make a reduced picture for the announcement. So I see two options:

1. Make these fields multiple. How?
   
2. Add multiple properties "Additional detailed pictures" and "Additional pictures for announcement". In this case, you need to reduce the image using the CFile::ResizeImageFile() function. But questions arise: Where is it better to do this (in a component, a component template, or somewhere else)? How to save data to infoblock from code?
   

Can you please tell me the best way to approach this task?