Viewer and Converter for Images

ImageMagick is a robust collection of tools and libraries to read,
write, and manipulate an image in many image formats, including popular
formats like TIFF, JPEG, PNG, PDF, PhotoCD, and GIF. With ImageMagick,
you can create images dynamically, making it suitable for Web
applications. You can also resize, rotate, sharpen, color-reduce, or
add special effects to an image and save your completed work in many
different image formats. Image processing operations are available from
the command line as well as through C, C++, and PERL-based programming
interfaces.