Manual threshold an image based on drawn shapes?

Hi all, I’m currently using ImageJ. Is there a way to set all pixels within a manually drawn shape to 0 (fully dark), and all other pixels outside the drawn shape to 1/255 (fully bright)? Basically manually thresholding the image based on a drawn polygon. Thank you!

Once you’ve drawn your polygon selection you can go to Process > Math > Set and set any value you want in there to be applied to the pixels in your selection.

I’m not sure what you want to do with the outside from your question but if you go to Edit > Selection > Make Inverse then everything outside of your shape will be selected so you can do the same process as above to change those pixels values.