ImageMagick is a free software project (with an Apache-like license) that supports about 100 image formats and format conversions. ImageMagick is also capable of doing a number of sophisticated things to images. For more details, check out its home page (http://www.imagemagick.org/).
ImageMagick is normally called from a terminal or command line, but its functionalities can also be accessed from other programs. When using it to process many files, you’ll find the filename globbing facilities of GNU/Linux extremely useful. For example, the command
convert *.jpg animation.gif
converts all the files in the current folder with a
.jpg suffix to a single GIF animation called
animation.gif. The asterisk is a wildcard, ...