If you are on Linux I recommend imagemagick. A powerful command line tool:
http://www.imagemagick.org/Usage/crop/#crop
to crop a single image to 95% width and height:
Code:
convert -gravity center -crop 95%x95+0+0 pic.jpg cropped_pic.jpg
to crop all jpg-files in a folder:
Code:
for img in $(ls *.jpg); do convert -gravity center -crop 95%x95+0+0 $img cropped${img%.*}.jpg; done;