David, I don't have the technical knowhow for proper image capturing from a DVD, although I thought there were controls in some players that allow exactly that.
However, perhaps it would be sufficient to simply pause on the required images and take a standard photo of the screen and work from there? Or just use standard pc controls for image capture, as below?
As an experiment, here's an image I took (without permisssion !!) from a rather good DVD on British Birds:
http://glassgallery.yobunny.org.uk/displayimage.php?pos=-2316I ran the video via Windows Media Player (to keep it basic), paused the play then used Alt + Prnt Scr to capture the DVD window. After resizing the captured image to 500 pixels width and sharpening, I optimised it from over 200Kb to around 50K. The full-sized result is not too different in quality from the actual paused DVD image.