VBA to save or extract background image

I need to use VBA to save the background image out of excel sheets. I can us "ActiveSheet.SetBackgroundPicture Filename:=bgPath" to set a background picture, but can't find a function to extract or save it.

I built an add-in that makes it easy to modify the colors of excel sheets. Part of that is creating a shape of selected color and setting it as a background image, which allows switching a sheet between "dark mode" and "light mode" without turning on high contrast. Everything works great, but I'm building an "invert colors" function and want to be able to invert the background image color. This isn't an issue when I set the background image and then invert in the same session as I can record the original color. Opening a saved file that already has the background set, however, requires me to extract the background image to invert the color.