browser cache - Firefox, saving all images from every page so that they are retrievable?

I'm having a bit of trouble finding a way to do this, I know that firefox saves images to a cache file but it is in a gzip archive file that I am unable to unzip (just gives error when I try, I'm using Ubuntu, so yes i do have gzip support).. I have looked for plugsin to do this but haven't found anything of use.. I want it so that, for every page I visit that all images on the page are automatically saved so as to be usable in the future.. if there is a way to get the images from the cache I would appreciate any advice to point me in the right direction.. thanks for any info