If you want to extract some images from a photo cd or dvd you can use transcode.
Installation
aptitude install transcode
Extract the images
transcode -x mpeg2 -i VTS_01_1.VOB -y im -F jpg -w 100
The parameters:
-F: picture format (jpg, gif, png) -w: quality for jpeg and compression-level
Links
* http://dvd-slideshow.sourceforge.net/wiki/FAQ_Extract_Images_From_Vob