Add-ons • Re: is there an addon to rip content protected images?

It's possible that in the case described by the OP, the image (img or canvas) is obscured by some transparent element

Yes, very common of course, but easy enough to get around. The more annoying ones are where JavaScript intercepts the right click. And Pale Moon causes a page refresh when disabling JavaScript, which often prevents the image from assembling properly...

Always a fun time.

A screenshot is often the ultimate solution, but of course the OP is looking for something else.