Resizing and editing multiple photos in Linux

One of the easiest ways to manipulate a multitude of images inside Linux is by using the Imagemagick suite of tools, particularly the 'convert' tool. To install imagemagick on an ubuntu system:

$ apt-get install imagemagick

Then you can use the convert command tool to execute massive image edits. For example to resize all images in a folder to 25%, you can use the following command:

$ for img in `ls *`; do convert $img -resize 25% "fb_"$img; done

I suggest you to take a look at the manual page of convert which is very informative.