I drew an oil painting based on a photo taken online. Is it infringement?

According to relevant laws, it is an infringement to process/copy/use related works of art without the permission of the copyright owner. There is also a general copyright law in the world, and China has also recognized this law.

If this work is very important to you, I suggest you get the written permission of the copyright owner first to avoid unnecessary trouble.

The above is only legal. But the practice of domestic art circles is that as long as it is not used for profit, it can be used; In fact, few people pursue this responsibility, for one thing, it is too troublesome, and for another, infringement actually has a promotional effect. Foreign countries are more serious in this respect. If there is infringement, it is likely to go to court.