LibRaw is a library for reading RAW files obtained from digital photo cameras (CRW/CR2, NEF, RAF, DNG, and others). LibRaw is based on the source codes of the dcraw utility, though some of the drawbacks of dcraw have been eliminated. The users of the library are provided with an API to be used when writing their software programs.
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.
pngquant is a batch conversion utility to quantize and dither truecolor PNG images, especially those with a full alpha channel, down to "RGBA-palette" PNGs (i.e., PLTE + tRNS in PNG parlance). Such images are usually two to four times smaller than the full 32-bit versions, and partial transparency is preserved quite nicely. This makes pngquant especially useful both for Web sites and for PlayStation 2 development, where one of the texture formats is RGBA-palette-based (though not PNG-compressed).
view3dscene is a browser for VRML (1.0 and 2.0) and X3D, and a viewer for other 3D model formats (3DS, MD3, Wavefront OBJ, and Collada are handled). It supports viewing the scene in the "Examine" mode and walking in the virtual world with features such as collision detection and gravity. Rendering is done using OpenGL. Many advanced 3D graphic effects are available, like mirrors (flat and through cube environment mapping), shadows (shadow maps and shadow volumes), GLSL shaders and more. The program can also convert files from 3DS, MD3, Collada and other formats to X3D and pretty-print VRML and X3D files.
pngcrush is an excellent batch-mode compression utility for PNG images. Depending on the application that created the original PNGs, it can improve the file size anywhere from a few percent to 40% or more (completely losslessly). The utility also allows specified PNG chunks (e.g. text comments) to be inserted or deleted, and it can fix incorrect gamma info written by Photoshop 5.0 as well as the erroneous iCCP chunk written by Photoshop 5.5.
BRL-CAD is a powerful constructive solid geometry solid modeling system that includes an interactive geometry editor, ray-tracing support for rendering and geometric analysis, path-tracing for realistic image synthesis, network distributed framebuffer support, and image and signal-processing tools.
Jitac is a Java application that converts images into ASCII art by associating blocks of the image with ASCII characters. It supports several image formats (GIF, JPEG, TIFF, and PNG) and some image manipulations that can be performed before the conversion (inversion, grayscale, resize, and gamma correction).