ImageMagick, is a collection of GUI and command line tools along with callable libraries allows you to read, write, and manipulate images in any of the more popular image formats including GIF, JPEG, TIFF, PNG and PDF.
There are two methods for accessing the capabilities of ImageMagick. Firstly you can incorporate its functionality directly into your own code by linking to the ImageMagick libraries, you can do this from several languages, including Perl, C, C++, Java and Python. More information can be found in the ImageMagick Users Guide .
You can also access ImageMagick functions directly from the command line using the display, import, animate, montage, convert, mogrify, identify, and combine tools. These tools allow powerful manipulations to be carried out on images in a manner understandable to anyone familiar with the UNIX way of doing things, for instance:
% convert file.jpg HISTOGRAM:- | display -
pipes the output of convert into the display application
to get a intensity histogram for the image file.jpg. Here the
use of ``-'' for the file specifier (for both convert and
display) directs the applications to use standard input and
output (i.e. streams).
The Graphics Cookbook