@Asiankarebear Are you taking the images directly from bilibili? If so, you don't actually need to SS them, as it's actually possible to get the original image.
Well, of course it is not as easy as "right click and save", but it's not hacker thingy either. Heck, all you need is a PC, or something equal that can use desktop browser (and some patience).
As for the software, you can try GIMP. It's free, quite lightweight, and has layer image editing, which is what you need. Edit the image on the top of it, save it while you edit them as layer-supported file (I forgot if it support PSD), and when you done, save it as JPG or PNG.
You only get one time compression loss (JPG), or no loss (PNG).
In fact, I'll DM you the images for chapter 17 that I fetch from bilibili. Whether you gonna use them, I'll leave that up to you 😀