Ghostscript is a processor for PostScript and PDF files. It can rasterize these files to a wide variety of printers, devices for screen preview, and image file formats. Since applications tend to prepare pages for printing in a high-level format such as PostScript, most Unix users with low-level bitmap printers, such as inkjets, use GhostScript as part of the printing process. In addition, Ghostscript is capable of converting PostScript files, functionality comparable to Adobe Acrobat Distiller, but on the command line. In addition, Ghostscript is used for file import and viewing by a great many other applications, including xv, ImageMagick, gimp, and xdvi. Several GUI wrappers for viewing PostScript and PDF files exist, including GSview, ghostview, gv, ggv, and kghostview. This is far from a comprehensive list.
GraphicsMagick is a robust collection of tools and libraries which support reading, writing, and manipulating an image in over 90 major formats including popular formats like DPX, DICOM, BMP, GIF, JPEG, JPEG-2000, PDF, PNG, PNM, SVG, and TIFF. A high-quality 2D renderer is included, which provides a subset of SVG capabilities. C, C++, Perl, Tcl, and Ruby are supported. Originally based on ImageMagick, GraphicsMagick focuses on performance, minimizing bugs, and providing stable APIs and ABIs. It runs on all modern variants of Unix, Windows, and Mac OS X.
UFRaw is a utility for converting and manipulating raw images from digital cameras. It can be used as a stand-alone tool or as a Gimp plugin, and images can be batch processed using the commandline interface. UFRaw reads most existing raw formats using Dave Coffin's raw conversion utility DCRaw, and it supports basic color management using Little CMS, allowing the user to apply color profiles. For Nikon users, UFRaw has the advantage that it can read the camera's tone curves. Even if you don't own a Nikon, you can still apply a Nikon curve to your images.
JBIG-KIT implements a highly effective data compression algorithm for bi-level high-resolution images such as fax pages or scanned documents. It provides a portable C library of compression and decompression functions with a documented interface that can easily be included into image or document processing software. In addition, JBIG-KIT provides ready-to-use compression and decompression programs with a simple command line interface (similar to the converters found in netpbm). It implements the specification ISO 11544 and ITU-T T.82, which is commonly referred to as the "JBIG1 standard".
Potrace is a utility for tracing a bitmap (that is, transforming a bitmap into a smooth, scalable image). The input is a portable bitmap (PBM), and the default output is an encapsulated PostScript file (EPS). A typical use is to create EPS files from scanned data, such as company or university logos, handwritten notes, etc. The resulting image is not "jaggy" like a bitmap, but smooth. It can then be rendered at any resolution.
Prima is an extensible Perl toolkit for multi-platform GUI development. Supported platforms include Linux, Windows NT/9x/2K, OS/2, and UNIX/X11 workstations (FreeBSD, IRIX, SunOS, Solaris, and others). The toolkit contains a rich set of standard widgets and has emphasis on 2D image processing tasks. A Perl program using Prima looks and behaves identically on X, Win32, and OS/2 PM.