I thought this was a very good question, so I tried it, and found success the first whack.
Using QT 5, I opened a video clip in .MOV format. There is a function in QT's menu that is COPY. Open in parallel, any good graphic program that accepts bitmapped images. I used HiJaak Pro 5.1. I hit the QT pause button, then COPY. Then I moved over to the graphics program and hit PASTE. In a few seconds, the frame was pasted.
Back to QT, then I ran a bit and repeated the process. It works. You can copy and paste frames as often as you like.
These were MOV video clips. Fun stuff!