I just made a post copy-pasting images from another tab. All jpegs became pngs, for example 1.3MB became 6.4MB.
If I save the image first, then upload to Lemmy, it stays as a jpeg. What causes the pointless converting when copy-pasting? Can it be stopped from happening?
No. When you copy an image like that you’re copying the image data to your clipboard, not the file.