Imported image showing HUGE file size compared to original image

I was dragging images into GIMP and noticed that GIMP indicated an image file size that was orders of magnitude higher than the original imported image. See pictures for context.

Screenshot 2023-07-12 at 9.32.53 PM

This is normal.

images in files are usually compressed, and PNG compresses screenshots very efficiently. Gimp shows you how much memory it needs to have the image uncompressed in memory, typically,

  • four bytes per pixel per layer (and one more if there is a layer mask),
  • the selection mask,
  • any channels,
  • a buffer for the output,
  • whatever is needed for undo steps, that can be full copies of layers

And this for 8-bit mode, multiply by four in high-precision mode.

Image > Properties gives you a bit more detail on memory usage.

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