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git-svn-id: svn+ssh://svn.code.sf.net/p/libjpeg-turbo/code/trunk@778 632fc199-4ca6-4c93-a231-07263d6284db
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README-turbo.txt
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@@ -3,31 +3,31 @@
******************************************************************************* *******************************************************************************
libjpeg-turbo is a derivative of libjpeg that uses SIMD instructions (MMX, libjpeg-turbo is a derivative of libjpeg that uses SIMD instructions (MMX,
SSE2, etc.) to accelerate baseline JPEG compression and decompression on x86 SSE2, NEON) to accelerate baseline JPEG compression and decompression on x86,
and x86-64 systems. On such systems, libjpeg-turbo is generally 2-4x as fast x86-64, and ARM systems. On such systems, libjpeg-turbo is generally 2-4x as
as the unmodified version of libjpeg, all else being equal. fast as the unmodified version of libjpeg, all else being equal.
libjpeg-turbo was originally based on libjpeg/SIMD by Miyasaka Masaru, but libjpeg-turbo was originally based on libjpeg/SIMD by Miyasaka Masaru, but
the TigerVNC and VirtualGL projects made numerous enhancements to the codec in 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 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 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 encoding/decoding, and various bug fixes. The goal was to produce a fully
source codec that could replace the partially closed source TurboJPEG/IPP codec open-source codec that could replace the partially closed-source TurboJPEG/IPP
used by VirtualGL and TurboVNC. libjpeg-turbo generally performs in the range codec used by VirtualGL and TurboVNC. libjpeg-turbo generally achieves 80-120%
of 80-120% of TurboJPEG/IPP. It is faster in some areas but slower in others. 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 In early 2010, libjpeg-turbo spun off into its own independent project, with
the goal of making high-speed JPEG compression/decompression technology the goal of making high-speed JPEG compression/decompression technology
available to a broader range of users and developers. The libjpeg-turbo shared available to a broader range of users and developers.
libraries can be used as drop-in replacements for libjpeg on most systems.
******************************************************************************* *******************************************************************************
** License ** License
******************************************************************************* *******************************************************************************
libjpeg-turbo is licensed under a non-restrictive, BSD-style license Most of libjpeg-turbo inherits the non-restrictive, BSD-style license used by
(see README.) The TurboJPEG/OSS wrapper (both C and Java versions) and libjpeg (see README.) The TurboJPEG/OSS wrapper (both C and Java versions) and
associated test programs bear a similar license, which is reproduced below: associated test programs bear a similar license, which is reproduced below:
Redistribution and use in source and binary forms, with or without Redistribution and use in source and binary forms, with or without
@@ -62,14 +62,14 @@ POSSIBILITY OF SUCH DAMAGE.
libjpeg-turbo includes two APIs that can be used to compress and decompress libjpeg-turbo includes two APIs that can be used to compress and decompress
JPEG images: JPEG images:
TurboJPEG API: This API wraps libjpeg-turbo and provides an easy-to-use TurboJPEG API: This API provides an easy-to-use interface for compressing
interface for compressing and decompressing JPEG images in memory. It also and decompressing JPEG images in memory. It also provides some functionality
provides some features that would not be straightforward to implement using that would not be straightforward to achieve using the underlying libjpeg
the underlying libjpeg API, such as generating planar YUV images and API, such as generating planar YUV images and performing multiple
performing multiple simultaneous lossless transforms on an image. The Java simultaneous lossless transforms on an image. The Java interface for
interface for libjpeg-turbo is written on top of the TurboJPEG API. 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 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 API but also more powerful. libjpeg-turbo is both API/ABI-compatible and
mathematically compatible with libjpeg v6b. It can also optionally be mathematically compatible with libjpeg v6b. It can also optionally be
@@ -101,13 +101,13 @@ NOTE: {lib} can be lib, lib32, lib64, or lib/64, depending on the O/S and
architecture. architecture.
System administrators can also replace the libjpeg sym links in /usr/{lib} with 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 links to the libjpeg-turbo dynamic library located in /opt/libjpeg-turbo/{lib}.
will effectively accelerate every dynamically linked libjpeg application on the This will effectively accelerate every application that uses the libjpeg
system. dynamic library on the system.
The libjpeg-turbo SDK for Visual C++ installs the libjpeg-turbo DLL 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 (jpeg62.dll, jpeg7.dll, or jpeg8.dll, depending on whether it was built with
v8 emulation is enabled) into c:\libjpeg-turbo[64]\bin, and the PATH 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 environment variable can be modified such that this directory is searched
before any others that might contain a libjpeg DLL. However, if a libjpeg 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 DLL exists in an application's install directory, then Windows will load this
@@ -117,16 +117,16 @@ version of this DLL and copy c:\libjpeg-turbo[64]\bin\jpeg*.dll into the
application's install directory to accelerate it. application's install directory to accelerate it.
The version of the libjpeg-turbo DLL distributed in the libjpeg-turbo SDK for 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 msvcr90.dll ships with more recent versions of Windows, but users of older
Windows releases can obtain it from the Visual C++ 2008 Redistributable Windows releases can obtain it from the Visual C++ 2008 Redistributable
Package, which is available as a free download from Microsoft's web site. 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 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 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 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(). jpeg_stdio_src().
Mac applications typically embed their own copies of the libjpeg dylib inside Mac applications typically embed their own copies of the libjpeg dylib inside
@@ -146,7 +146,7 @@ Replacing TurboJPEG/IPP
libjpeg-turbo is a drop-in replacement for the TurboJPEG/IPP SDK used by 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 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 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 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 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 at run time. Note that the 64-bit libjpeg-turbo packages contain only 64-bit
@@ -157,7 +157,7 @@ both the 64-bit and 32-bit versions of libjpeg-turbo.
You can also build the VirtualGL 2.1.x and TurboVNC 0.6 source code with 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. the libjpeg-turbo SDK instead of TurboJPEG/IPP. It should work identically.
libjpeg-turbo also includes static library versions of TurboJPEG/OSS, which 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 Using libjpeg-turbo in Your Own Programs
@@ -342,12 +342,13 @@ Restart Markers
=============== ===============
The optimized Huffman decoder in libjpeg-turbo does not handle restart markers 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 in a way that makes the rest of the libjpeg infrastructure happy, so it is
decoder when decompressing a JPEG image that has restart markers. This can necessary to use the slow Huffman decoder when decompressing a JPEG image that
cause the decompression performance to drop by as much as 20%, but the has restart markers. This can cause the decompression performance to drop by
performance will still be much much greater than that of libjpeg v6b. Many as much as 20%, but the performance will still be much greater than that of
consumer packages, such as PhotoShop, use restart markers when generating JPEG libjpeg. Many consumer packages, such as PhotoShop, use restart markers when
images, so images generated by those programs will experience this issue. generating JPEG images, so images generated by those programs will experience
this issue.
=============================================== ===============================================
Fast Integer Forward DCT at High Quality Levels Fast Integer Forward DCT at High Quality Levels