Imagemagick and ffmpeg can extract single frames from movies. If you manage to install Image::Magick or the forked and supposedly more stable GraphicsMagick, you can access an .mpg stream as an array of images.

I would go the easier way of using an external program to extract the images, like the convert program that comes with ImageMagick or GraphicsMagick, or ffmpeg.

One random commandline I found for ffmpeg via Google was:

ffmpeg -i swing.avi -vcodec png -vframes 1 -an -f rawvideo -s 320x240 
+swing1.png
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