I’m using a camlink to connect a Nikon camera to my PC, but you could use your webcam also for this trick.
Now i can activate the full screen projector in OBS to preview and sort the negatives on a big screen. (right click on you preview screen)
When connecting a camera to OBS you initially have a “negative” image.
Below trick inverts your image, after that you can use your camera controls or OBS colour correction filter to adjust.
I’m using gimp to invert the LUT png image, but most image editors can invert an image.
A LUTs is a LookUp Table. Color presets/filters for adjusting the image.
Hardcore method .. command line
convert input.png -channel RGB -negate invert.png