Change screenshot format iOS

Of course I already do that. The issue is, I have WhatsApp on my Mac, and if I want to send a photo as an attachment with a message, when I select 'Photos' as the source of the photo I want to send, when I navigate to 'Photos,' any screenshots I took with the iPad don't show up in the window, even though they're present in the Photos app (which of course I sync using the Cloud between my iPad and my Mac). I have to drag the photo out of the Photos app to the desktop on the Mac, remove the 'e' from the suffix '.jpeg,' and only then will WhatsApp see the photo in question. If I could set the ipad to save all screenshots as .png, for example, it would solve the problem. It's not a case of the photo being accessible on my Apple devices, it's a case of WhatsApp (for example) seeing the photos that were taken as screenshots on the iPad.

When you say 'automatically," how does it decide? Because lately it seems all my screenshots are being saved as .jpeg format. Must say I never could quite understand why there are both .jpg and .jpeg anyway. It would be great if I could find a setting that I could set to make it always use .png, or indeed simply .jpg.