I see that Grim Dawn creates a folder automatically in the documents folder for screenshots:
e.g. "D:\Documents\My Games\Grim Dawn\Screenshots"

By pressing the [PrtScn] key it will put screen captures in the folder... but the format is JPG.

Does anyone know of a way to force Grim Dawn to use the PNG format for screenshots (or another lossless format)?

I was hoping to be able to do this with my GOG.com version... as I know I can always run it through Steam, as a non-Steam game, then hit F12 with the option to "save an uncompressed copy" of screenshots to a Steam folder as a work-around.

Thanks for any help! Cheers :)

As it is put in game code there is probably no way to force game to save as another format. Though if screenshot is a good one you can also [Alt]+[Tab] game and make png yourself, as [PrtSc] also put an image in your pc memory, so You can create your own image in every single graphic program (even paint).