If you can view the image on your laptop from the HTML, you should be able to right-click over the image and select "Save Picture as..." you can then save the image itself to a location of your choice such as desktop. You then can sign on to FB and navigate to desktop and post it.
BTW: I have posted JPG, BMP, and PNG image files without any issues on FB, so I know for a fact that those 3 image types are supported.