libjpeg-turbo | Documentation / Installing libjpeg-turbo on Cygwin

NOTE: As of version 1.5 beta1, The libjpeg-turbo Project is no longer providing "official" binary packages for Cygwin, since Cygwin and Cygwin64 are now supplying their own libjpeg-turbo packages. Thus, these instructions apply only to libjpeg-turbo 1.4.2 and prior.

The 32-bit Cygwin environment has traditionally not included libjpeg-turbo and, as of this writing, still doesn't (although Cygwin64 does.) Regardless, even if libjpeg-turbo were included in Cygwin, it would still be desirable at times to use a newer version of libjpeg-turbo than the one that Cygwin includes. For these reasons, we have been providing our own "official" Cygwin packages since libjpeg-turbo 1.0.0. Traditionally, it was possible (although not necessarily straightforward) to install these packages from a local directory using the Cygwin setup program. However, more recent versions of Cygwin setup now require that a setup.ini file exist for any binary packages that will be installed, even if the install is being performed from a local directory. Rather than deal with this, it was just easier to set up our own Cygwin repository. This article describes how to use our custom Cygwin repository to install a release or pre-release of libjpeg-turbo.

Download either setup-x86.exe or setup-x86_64.exe from http://www.cygwin.com, depending on whether you want to install a 32-bit or a 64-bit version of libjpeg-turbo.
Execute the following from a Command Prompt:
```
setup-x86[_64].exe -X
```
(The -X option is necessary because our repository's setup.ini file is not signed with the Cygwin GPG key.)
On the "Choose Download Site(s)" screen, enter one of the following URLs in the "User URL" box, then click "Add":

libjpeg-turbo Releases: http://sourceforge.net/projects/libjpeg-turbo/files/cygwin

libjpeg-turbo Pre-Releases: http://libjpeg-turbo.sourceforge.net/ljt.nightly/cygwin

NOTE: Cygwin packages are not always available with every pre-release. Check for a cygwin/ directory in the pre-release directory (see http://www.libjpeg-turbo.org/DeveloperInfo/PreReleases.) If there are multiple pre-releases available, then one of them may have a different URL than the above, such as libjpeg-turbo.sourceforge.net/ljt.nightly.{branch}/cygwin.
The "Select Packages" screen should now appear, with a "libjpeg-turbo" category and one package ("libjpeg-turbo-official") under that category. As with any other Cygwin package, you can click on the version number to cycle through the various versions available for install, as well as to choose the "Uninstall" and "Reinstall" options.

You can also automate the installation somewhat by using the following command line:

setup-x86[_64].exe -X -M -n -L -l {local_cache} -D -O -s {repository_URL}

where {local_cache} is the directory in which Cygwin setup should store downloaded packages, and {repository_URL} is one of the URLs listed above. Run setup-x86[_64].exe -h for a description of what these various command-line options do.