*******************************************************************************
libjpeg-turbo is a derivative of libjpeg that uses SIMD instructions (MMX,
-SSE2, etc.) to accelerate baseline JPEG compression and decompression on x86
-and x86-64 systems. On such systems, libjpeg-turbo is generally 2-4x as fast
-as the unmodified version of libjpeg, all else being equal.
+SSE2, NEON) to accelerate baseline JPEG compression and decompression on x86,
+x86-64, and ARM systems. On such systems, libjpeg-turbo is generally 2-4x as
+fast as the unmodified version of libjpeg, all else being equal.
libjpeg-turbo was originally based on libjpeg/SIMD by Miyasaka Masaru, but
the TigerVNC and VirtualGL projects made numerous enhancements to the codec in
2009, including improved support for Mac OS X, 64-bit support, support for
-32-bit and big endian pixel formats (RGBX, XBGR, etc.), accelerated Huffman
-encoding/decoding, and various bug fixes. The goal was to produce a fully open
-source codec that could replace the partially closed source TurboJPEG/IPP codec
-used by VirtualGL and TurboVNC. libjpeg-turbo generally performs in the range
-of 80-120% of TurboJPEG/IPP. It is faster in some areas but slower in others.
+32-bit and big-endian pixel formats (RGBX, XBGR, etc.), accelerated Huffman
+encoding/decoding, and various bug fixes. The goal was to produce a fully
+open-source codec that could replace the partially closed-source TurboJPEG/IPP
+codec used by VirtualGL and TurboVNC. libjpeg-turbo generally achieves 80-120%
+of the performance of TurboJPEG/IPP. It is faster in some areas but slower in
+others.
In early 2010, libjpeg-turbo spun off into its own independent project, with
the goal of making high-speed JPEG compression/decompression technology
-available to a broader range of users and developers. The libjpeg-turbo shared
-libraries can be used as drop-in replacements for libjpeg on most systems.
+available to a broader range of users and developers.
*******************************************************************************
** License
*******************************************************************************
-libjpeg-turbo is licensed under a non-restrictive, BSD-style license
-(see README.) The TurboJPEG/OSS wrapper (both C and Java versions) and
+Most of libjpeg-turbo inherits the non-restrictive, BSD-style license used by
+libjpeg (see README.) The TurboJPEG/OSS wrapper (both C and Java versions) and
associated test programs bear a similar license, which is reproduced below:
Redistribution and use in source and binary forms, with or without
libjpeg-turbo includes two APIs that can be used to compress and decompress
JPEG images:
- TurboJPEG API: This API wraps libjpeg-turbo and provides an easy-to-use
- interface for compressing and decompressing JPEG images in memory. It also
- provides some features that would not be straightforward to implement using
- the underlying libjpeg API, such as generating planar YUV images and
- performing multiple simultaneous lossless transforms on an image. The Java
- interface for libjpeg-turbo is written on top of the TurboJPEG API.
+ TurboJPEG API: This API provides an easy-to-use interface for compressing
+ and decompressing JPEG images in memory. It also provides some functionality
+ that would not be straightforward to achieve using the underlying libjpeg
+ API, such as generating planar YUV images and performing multiple
+ simultaneous lossless transforms on an image. The Java interface for
+ libjpeg-turbo is written on top of the TurboJPEG API.
- libjpeg API: This is the industry standard API for compressing and
+ libjpeg API: This is the de facto industry-standard API for compressing and
decompressing JPEG images. It is more difficult to use than the TurboJPEG
API but also more powerful. libjpeg-turbo is both API/ABI-compatible and
mathematically compatible with libjpeg v6b. It can also optionally be
architecture.
System administrators can also replace the libjpeg sym links in /usr/{lib} with
-links to the libjpeg dynamic library located in /opt/libjpeg-turbo/{lib}. This
-will effectively accelerate every dynamically linked libjpeg application on the
-system.
+links to the libjpeg-turbo dynamic library located in /opt/libjpeg-turbo/{lib}.
+This will effectively accelerate every application that uses the libjpeg
+dynamic library on the system.
The libjpeg-turbo SDK for Visual C++ installs the libjpeg-turbo DLL
-(jpeg62.dll, jpeg7.dll, or jpeg8.dll, depending on whether libjpeg v6b, v7, or
-v8 emulation is enabled) into c:\libjpeg-turbo[64]\bin, and the PATH
+(jpeg62.dll, jpeg7.dll, or jpeg8.dll, depending on whether it was built with
+libjpeg v6b, v7, or v8 emulation) into c:\libjpeg-turbo[64]\bin, and the PATH
environment variable can be modified such that this directory is searched
before any others that might contain a libjpeg DLL. However, if a libjpeg
DLL exists in an application's install directory, then Windows will load this
application's install directory to accelerate it.
The version of the libjpeg-turbo DLL distributed in the libjpeg-turbo SDK for
-Visual C++ requires the Visual C++ 2008 C run time DLL (msvcr90.dll).
+Visual C++ requires the Visual C++ 2008 C run-time DLL (msvcr90.dll).
msvcr90.dll ships with more recent versions of Windows, but users of older
Windows releases can obtain it from the Visual C++ 2008 Redistributable
Package, which is available as a free download from Microsoft's web site.
-NOTE: Features of libjpeg that require passing a C run time structure, such
+NOTE: Features of libjpeg that require passing a C run-time structure, such
as a file handle, from an application to libjpeg will probably not work with
the version of the libjpeg-turbo DLL distributed in the libjpeg-turbo SDK for
Visual C++, unless the application is also built to use the Visual C++ 2008 C
-run time DLL. In particular, this affects jpeg_stdio_dest() and
+run-time DLL. In particular, this affects jpeg_stdio_dest() and
jpeg_stdio_src().
Mac applications typically embed their own copies of the libjpeg dylib inside
libjpeg-turbo is a drop-in replacement for the TurboJPEG/IPP SDK used by
VirtualGL 2.1.x and TurboVNC 0.6 (and prior.) libjpeg-turbo contains a wrapper
library (TurboJPEG/OSS) that emulates the TurboJPEG API using libjpeg-turbo
-instead of the closed source Intel Performance Primitives. You can replace the
+instead of the closed-source Intel Performance Primitives. You can replace the
TurboJPEG/IPP package on Linux systems with the libjpeg-turbo package in order
to make existing releases of VirtualGL 2.1.x and TurboVNC 0.x use the new codec
at run time. Note that the 64-bit libjpeg-turbo packages contain only 64-bit
You can also build the VirtualGL 2.1.x and TurboVNC 0.6 source code with
the libjpeg-turbo SDK instead of TurboJPEG/IPP. It should work identically.
libjpeg-turbo also includes static library versions of TurboJPEG/OSS, which
-are used to build TurboVNC 1.0 and later.
+are used to build VirtualGL 2.2 and TurboVNC 1.0 and later.
========================================
Using libjpeg-turbo in Your Own Programs
===============
The optimized Huffman decoder in libjpeg-turbo does not handle restart markers
-in a way that makes libjpeg happy, so it is necessary to use the slow Huffman
-decoder when decompressing a JPEG image that has restart markers. This can
-cause the decompression performance to drop by as much as 20%, but the
-performance will still be much much greater than that of libjpeg v6b. Many
-consumer packages, such as PhotoShop, use restart markers when generating JPEG
-images, so images generated by those programs will experience this issue.
+in a way that makes the rest of the libjpeg infrastructure happy, so it is
+necessary to use the slow Huffman decoder when decompressing a JPEG image that
+has restart markers. This can cause the decompression performance to drop by
+as much as 20%, but the performance will still be much greater than that of
+libjpeg. Many consumer packages, such as PhotoShop, use restart markers when
+generating JPEG images, so images generated by those programs will experience
+this issue.
===============================================
Fast Integer Forward DCT at High Quality Levels
projects / libjpeg-turbo / commitdiff