GraphicsMagick is the swiss army knife of image processing. It provides a robust collection of tools and libraries which support reading, writing, and manipulating an image in over 88 major formats including important formats like DPX, GIF, JPEG, JPEG-2000, PNG, PDF, SVG, and TIFF. GraphicsMagick
... [More] supports huge images on systems that support large files, and has been tested with gigapixel-size images. GraphicsMagick can create new images on the fly, making it suitable for building dynamic Web applications. GraphicsMagick may be used to resize, rotate, sharpen, color reduce, or add special effects to an image and save the result in the same or differing image format. [Less]
FreeImage is an Open Source library project for developers who would like to support popular graphics image formats like PNG, BMP, JPEG, TIFF and others as needed by today's multimedia applications. FreeImage is easy to use, fast, multi threading safe, compatible with all 32-bit versions of Windows
... [More], and cross-platform (works both with Linux and Mac OS X). [Less]
The VIPS library/image processing system is well suited for larger than RAM true and false-colour images. VIPS can be used for image format conversion, colour calibration, image filtering, transformation and analysis, thumbnail generation, small object recognition and many other image processing
... [More] tasks. VIPS is well suited for medical and scientific research & development and batch image processing. It is not so good for retouching photographs. The system has two main parts: libvips is the library, and nip2 is the GUI. Both execute common image processing tasks faster than other image processing systems because of sophisticated memory/task management and multicore compatibility.
VIPS runs in batch (command line) mode on *nix, Windows, Mac and other OSes. [Less]