for this you need at least 2 third-party software, one to recognize the position of the pointer on the current active window, and a second that can generate a shortcut for the action that you want, but remember that a lot of webpages nowadays use a 'transperent' image overlay that covers the real image, so the users won't be able to 'save' the images, so if the user 'saves' a image, what they're saving actually is just a transparent image, generally a 16*16 square; if you got this issue, try saving the page using good 'ol > CRTL+S, then check the saved webpage folder, there should be your desired image
this is not a 'so-elegant' way to do it, but sometimes is easier to do this than a go for a more complicated approach