Various documentation tweaks

git-svn-id: https://libjpeg-turbo.svn.sourceforge.net/svnroot/libjpeg-turbo@387 3789f03b-4d11-0410-bbf8-ca57d06f2519

1 files changed, 64 insertions, 63 deletions

diff --git a/branches/1.1.x/README-turbo.txt b/branches/1.1.x/README-turbo.txt
index 33ed4cc..c346bc3 100755
--- a/branches/1.1.x/README-turbo.txt
+++ b/branches/1.1.x/README-turbo.txt
@@ -5,7 +5,7 @@
 libjpeg-turbo is a high-speed version of libjpeg for x86 and x86-64 processors
 which uses SIMD instructions (MMX, SSE2, etc.) to accelerate baseline JPEG
 compression and decompression.  libjpeg-turbo is generally 2-4x as fast
-as the unmodified version of libjpeg, all else being equal.
+as the unmodified version of libjpeg v6b, 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,
@@ -25,49 +25,21 @@ libraries can be used as drop-in replacements for libjpeg on most systems.
 **     License
 *******************************************************************************
 
-Some of the optimizations to the Huffman encoder (jchuff.c) and decoder
-(jdhuff.c) were borrowed from VirtualGL, and thus any distribution of
-libjpeg-turbo which includes those optimizations must, as a whole, be subject
-to the terms of the wxWindows Library Licence, Version 3.1.  A copy of this
-license can be found in this directory under LICENSE.txt.  The wxWindows
-Library License is based on the LGPL but includes provisions which allow the
-Library to be statically linked into proprietary libraries and applications
-without requiring the resulting binaries to be distributed under the terms of
-the LGPL.
+The TurboJPEG/OSS wrapper, as well as some of the optimizations to the Huffman
+encoder (jchuff.c) and decoder (jdhuff.c), were borrowed from VirtualGL, and
+thus any distribution of libjpeg-turbo which includes those files must, as a
+whole, be subject to the terms of the wxWindows Library Licence, Version 3.1.
+A copy of this license can be found in this directory under LICENSE.txt.  The
+wxWindows Library License is based on the LGPL but includes provisions which
+allow the Library to be statically linked into proprietary libraries and
+applications without requiring the resulting binaries to be distributed under
+the terms of the LGPL.
 
-The rest of the source code, apart from the Huffman codec optimizations, falls
-under a less restrictive, BSD-style license (see README.)  You can choose to
-distribute libjpeg-turbo, as a whole, under this BSD-style license by simply
-replacing the optimized jchuff.c and jdhuff.c with their unoptimized
-counterparts from the libjpeg v6b source.
-
-
-*******************************************************************************
-**     Performance pitfalls
-*******************************************************************************
-
-===============
-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
-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.
-
-===============================================
-Fast Integer Forward DCT at High Quality Levels
-===============================================
-
-The algorithm used by the SIMD-accelerated quantization function cannot produce
-correct results whenever the fast integer forward DCT is used along with a JPEG
-quality of 98-100.  Thus, libjpeg-turbo must use the non-SIMD quantization
-function in those cases.  This causes performance to drop by as much as 40%.
-It is therefore strongly advised that you use the slow integer forward DCT
-whenever encoding images with a JPEG quality of 98 or higher.
+The rest of the source code, apart from TurboJPEG/OSS and the Huffman codec
+optimizations, falls under a less restrictive, BSD-style license (see README.)
+You can choose to distribute libjpeg-turbo, as a whole, under this BSD-style
+license by simply removing TurboJPEG/OSS and replacing the optimized jchuff.c
+and jdhuff.c with their unoptimized counterparts from the libjpeg v6b source.
 
 
 *******************************************************************************
@@ -79,7 +51,7 @@ Replacing libjpeg at Run Time
 =============================
 
 If a Unix application is dynamically linked with libjpeg, then you can replace
-libjpeg with libjpeg-turbo at run time by manipulating the LD_LIBRARY_PATH.
+libjpeg with libjpeg-turbo at run time by manipulating LD_LIBRARY_PATH.
 For instance:
 
   [Using libjpeg]
@@ -103,28 +75,29 @@ links to the libjpeg dynamic library located in /opt/libjpeg-turbo/{lib}.  This
 will effectively accelerate every dynamically linked libjpeg application on the
 system.
 
-The Windows distribution of the libjpeg-turbo SDK 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
+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
 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
 DLL first whenever the application is launched.  Thus, if an application ships
 with jpeg62.dll, jpeg7.dll, or jpeg8.dll, then back up the application's
-version of this DLL and copy c:\libjpeg-turbo\bin\jpeg*.dll into the
+version of this DLL and copy c:\libjpeg-turbo[64]\bin\jpeg*.dll into the
 application's install directory to accelerate it.
 
-The version of the libjpeg-turbo DLL distributed with the "official"
-libjpeg-turbo SDK requires the Visual C++ 2008 C run time DLL (msvcr90.dll).
+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).
 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 which require passing a C run time structure, such
 as a file handle, from an application to libjpeg will probably not work with
-the "official" version of the libjpeg-turbo DLL unless the application is also
-built to use the Visual C++ 2008 C run time DLL.  In particular, this affects
-jpeg_stdio_dest() and jpeg_stdio_src().
+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
+jpeg_stdio_src().
 
 Mac applications typically embed their own copies of the libjpeg dylib inside
 the (hidden) application bundle, so it is not possible to globally replace
@@ -145,8 +118,8 @@ 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
 TurboJPEG/IPP package on Linux systems with the libjpeg-turbo package in order
-to make existing releases of VirtualGL 2.1.x and TurboVNC use the new codec at
-run time.  Note that the 64-bit libjpeg-turbo packages contain only 64-bit
+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
 binaries, whereas the TurboJPEG/IPP 64-bit packages contained both 64-bit and
 32-bit binaries.  Thus, to replace a TurboJPEG/IPP 64-bit package, install
 both the 64-bit and 32-bit versions of libjpeg-turbo.
@@ -180,11 +153,11 @@ If using MinGW, then set
 
 Building against libjpeg-turbo is useful, for instance, if you want to build an
 application that leverages the libjpeg-turbo colorspace extensions (see below.)
-On Linux and Solaris systems, you would still need to manipulate the
-LD_LIBRARY_PATH or sym links appropriately to use libjpeg-turbo at run time.
-On such systems, you can pass -R /opt/libjpeg-turbo/{lib} to the linker to
-force the use of libjpeg-turbo at run time rather than libjpeg (also useful if
-you want to leverage the colorspace extensions), or you can link against the
+On Linux and Solaris systems, you would still need to manipulate
+LD_LIBRARY_PATH or create appropriate sym links to use libjpeg-turbo at run
+time.  On such systems, you can pass -R /opt/libjpeg-turbo/{lib} to the linker
+to force the use of libjpeg-turbo at run time rather than libjpeg (also useful
+if you want to leverage the colorspace extensions), or you can link against the
 libjpeg-turbo static library.
 
 To force a Linux, Solaris, or MinGW application to link against the static
@@ -196,8 +169,8 @@ On OS X, simply add /opt/libjpeg-turbo/lib/libjpeg.a to the linker command
 line (this also works on Linux and Solaris.)
 
 To build Visual C++ applications using libjpeg-turbo, add
-c:\libjpeg-turbo[64]\include to your system or user INCLUDE environment
-variable and c:\libjpeg-turbo[64]\lib to your system or user LIB environment
+c:\libjpeg-turbo[64]\include to the system or user INCLUDE environment
+variable and c:\libjpeg-turbo[64]\lib to the system or user LIB environment
 variable, and then link against either jpeg.lib (to use the DLL version of
 libjpeg-turbo) or jpeg-static.lib (to use the static version of libjpeg-turbo.)
 
@@ -255,7 +228,7 @@ releases will also be backward-incompatible.
 
 By passing an argument of --with-jpeg7 or --with-jpeg8 to configure, or an
 argument of -DWITH_JPEG7=1 or -DWITH_JPEG8=1 to cmake, you can build a version
-of libjpeg-turbo which emulates the libjpeg v7 or v8b API/ABI, so that programs
+of libjpeg-turbo which emulates the libjpeg v7 or v8 API/ABI, so that programs
 which are built against libjpeg v7 or v8 can be run with libjpeg-turbo.  The
 following section describes which libjpeg v7+ features are supported and which
 aren't.
@@ -300,3 +273,31 @@ Not supported:
 
 -- jpegtran: Scaling
    Seems to depend on the DCT scaling feature, which isn't supported.
+
+
+*******************************************************************************
+**     Performance pitfalls
+*******************************************************************************
+
+===============
+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
+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.
+
+===============================================
+Fast Integer Forward DCT at High Quality Levels
+===============================================
+
+The algorithm used by the SIMD-accelerated quantization function cannot produce
+correct results whenever the fast integer forward DCT is used along with a JPEG
+quality of 98-100.  Thus, libjpeg-turbo must use the non-SIMD quantization
+function in those cases.  This causes performance to drop by as much as 40%.
+It is therefore strongly advised that you use the slow integer forward DCT
+whenever encoding images with a JPEG quality of 98 or higher.