Reference Links . A very neat part of Microsoft's site, navigated by a nice Java treeview showing the library contents.
Registration is no longer required - completely free.
IJG is an informal group that writes and distributes a widely used free library for JPEG image compression. The home page for the Portable Network Graphics file format, including the specs and C code. Download their free Zip and Unzip DLLs here. The compression algorithm used is essentially the same as used in PKZip and gzip. A nice, free, fully working OCX providing access to Zlib compression and decompression.