Change thumbnail from png to jpeg format

I am creating thumbnails from file manager. Generated thumnail is in .png format.

But problem is that it is .png format and also it take near 120-180 seconds to create thumnail and size is also very large near 4-5 MB

I am on E5-1650 dedicated server with 64 GB RAM.

How to change it in .jpg format

.png is lossless so it looks as good as it gets jpeg loses pixels. but i dont remember how to change it i know it’s in the screenshots settings in rutorrent but that’s all i could tell you right now

in screenshot setting it if only for single screenshot.

Look at how much time it take