curl and libcurl is a tool for transferring files using URL syntax. It supports HTTP, HTTPS, FTP, FTPS, SCP, SFTP, TFTP, DICT, TELNET, LDAP, POP3, IMAP, SMTP, RTSP, RTMP, and FILE, as well as HTTP-post, HTTP-put, cookies, FTP upload, resumed transfers, passwords, port numbers, SSL certificates, Kerberos, and proxies. It is powered by libcurl, the client-side URL transfer library. There are bindings to libcurl for about 40 languages and environments.
The Geospatial Data Abstraction Library (GDAL) is a unifying C/C++ API for accessing raster geospatial data, and currently includes formats like GeoTIFF, Erdas Imagine, Arc/Info Binary, CEOS, DTED, GXF, and SDTS. It is intended to provide efficient access, suitable for use in viewer applications, and also attempts to preserve coordinate systems and metadata. Python, C, and C++ interfaces are available.
libgeotiff is a library (normally built on top of libtiff) for reading and writing coordinate system information from/to GeoTIFF files. It includes CSV files for expanding projected coordinate system codes into full projections definitions and examples of transforming the definitions into a form that can be used with the PROJ.4 projections library. It also includes the sample applications listgeo (for dumping GeoTIFF information in readable form) and geotifcp (for applying geotiff tags to an existing TIFF or GeoTIFF file).
PROJ.4 is a cartographic projections and datum shifting library written in C. It includes support for many (100+) projections, including Transverse Mercator and Lambert Conformal Conic. Included is a command line program for reprojecting points. It was originally written by Gerald Evenden of the USGS, and is in active use in various commercial and freeware software.
ZooLib allows one to write a single set of C++ sources which can be compiled into native executables for Mac OS, Windows, BeOS, or POSIX-compliant systems that use the X Window system (such as Linux). Zoolib provides a GUI toolkit with a uniquely flexible layout system. It also provides a single-file database format, TCP networking, and extensive debugging support. ZooLib applications are multithreaded. ZooLib requires only minimal support from the underlying OS and platform GUI layer, and thus could be ported to a completely new platform without too much difficulty. ZooLib is fully production quality on Windows and MacOS, completely implemented but untested on BeOS, and not yet complete on POSIX. Please note that the sources from the "demo" branch are also required to build ZooLib or to get started writing your own ZooLib applications.
The JThread package contains classes that represent a thread and a mutex. On a Unix-like platform, the pthread library is used as the underlying thread mechanism. On an MS Windows platform, Win32 threads are used. By using these wrapper classes, you can easily create applications that use threads without having to worry about which platform the program will be running on.
freeglut is intended to be a 100% plug-compatible clone, and is released under the Xfree license. The GLUT (OpenGL Utility Toolkit) is a widely used library for doing window control, keyboard, and mouse input, and other basic functions for OpenGL programs. However, GLUT is not OpenSourced - although it's source code is available under a somewhat ill-defined set of restrictions. Hence, 'freeglut'.
Shapefile C Library is a C library for reading and writing ESRI Shapefiles and their related DBF files. All geometry types are supported, with robust DBF support. Shapelib is widely used for commercial and free projects. Shapelib includes command line utilities for dumping, subsetting, clipping, shifting, scaling, and reprojecting shapefiles.