Files
mozjpeg/release
DRC 4b67db4d9b rpm.spec.in: Fix doc packaging issues w/ RHEL 7+
On RHEL 7 and later (not sure exactly whether this is a product of the
newer RPM release or something distro-specific), macros are lazily
expanded, so we need to set _docdir using %global (which expands at
definition time) and prior to _prefix and _datarootdir (which affect
_defaultdocdir.)  Otherwise, _docdir is set to a subdirectory of
/opt/libjpeg-turbo/share/doc or /opt/libjpeg-turbo/doc.  The former
(which happens on RHEL 7) leads to incorrect documentation packaging
(the docs should be packaged under /usr/share/doc per Red Hat
standards), and the latter (which happens on RHEL 8) leads to an RPM
build error.
2019-02-13 17:04:28 -06:00
..

libjpeg-turbo is a JPEG image codec that uses SIMD instructions (MMX, SSE2, AVX2, NEON, AltiVec) to accelerate baseline JPEG compression and decompression on x86, x86-64, ARM, and PowerPC systems, as well as progressive JPEG compression on x86 and x86-64 systems.  On such systems, libjpeg-turbo is generally 2-6x as fast as libjpeg, all else being equal.  On other types of systems, libjpeg-turbo can still outperform libjpeg by a significant amount, by virtue of its highly-optimized Huffman coding routines.  In many cases, the performance of libjpeg-turbo rivals that of proprietary high-speed JPEG codecs.

libjpeg-turbo implements both the traditional libjpeg API as well as the less powerful but more straightforward TurboJPEG API.  libjpeg-turbo also features colorspace extensions that allow it to compress from/decompress to 32-bit and big-endian pixel buffers (RGBX, XBGR, etc.), as well as a full-featured Java interface.

libjpeg-turbo was originally based on libjpeg/SIMD, an MMX-accelerated derivative of libjpeg v6b developed by Miyasaka Masaru.  The TigerVNC and VirtualGL projects made numerous enhancements to the codec in 2009, and in early 2010, libjpeg-turbo spun off into an independent project, with the goal of making high-speed JPEG compression/decompression technology available to a broader range of users and developers.