Updates libjpeg-turbo to 1.1.90 (r677)

third_party/libjpeg_turbo/README-turbo.txt

 *******************************************************************************
 **     Background
 *******************************************************************************
 
-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
+libjpeg-turbo is a derivative of libjpeg which 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.
 
 libjpeg-turbo was originally based on libjpeg/SIMD by Miyasaka Masaru, but
-the TigerVNC and VirtualGL projects made numerous enhancements to the codec,
-including improved support for Mac OS X, 64-bit support, support for 32-bit
-and big endian pixel formats, 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.
+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.
 
-It was decided to split libjpeg-turbo into a separate SDK so that other
-projects could take advantage of this technology.  The libjpeg-turbo shared
+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.
 
 
 *******************************************************************************
 **     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.
+libjpeg-turbo is licensed under a non-restrictive, BSD-style license
+(see README.)  The TurboJPEG/OSS wrapper (both C and Java versions) and
+associated test programs bear a similar license, which is reproduced below:
 
-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.
+Redistribution and use in source and binary forms, with or without
+modification, are permitted provided that the following conditions are met:
+
+- Redistributions of source code must retain the above copyright notice,
+  this list of conditions and the following disclaimer.
+- Redistributions in binary form must reproduce the above copyright notice,
+  this list of conditions and the following disclaimer in the documentation
+  and/or other materials provided with the distribution.
+- Neither the name of the libjpeg-turbo Project nor the names of its
+  contributors may be used to endorse or promote products derived from this
+  software without specific prior written permission.
+
+THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS",
+AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ARE DISCLAIMED.  IN NO EVENT SHALL THE COPYRIGHT HOLDERS OR CONTRIBUTORS BE
+LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+POSSIBILITY OF SUCH DAMAGE.
 
 
 *******************************************************************************
 **     Using libjpeg-turbo
 *******************************************************************************
 
+libjpeg-turbo includes two APIs which can be used to compress and decompress
+JPEG images:
+
+  TurboJPEG/OSS:  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 TurboJPEG/OSS.
+
+  libjpeg API:  This is the industry standard API for compressing and
+  decompressing JPEG images.  It is more difficult to use than TurboJPEG/OSS
+  but also more powerful.  libjpeg-turbo is both API/ABI-compatible and
+  mathematically compatible with libjpeg v6b.  It can also optionally be
+  configured to be API/ABI-compatible with libjpeg v7 and v8 (see below.)
+
+
 =============================
 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]
   > time cjpeg <vgl_5674_0098.ppm >vgl_5674_0098.jpg
   real  0m0.392s
   user  0m0.074s
   sys   0m0.020s
 
   [Using libjpeg-turbo]
   > export LD_LIBRARY_PATH=/opt/libjpeg-turbo/{lib}:$LD_LIBRARY_PATH
   > time cjpeg <vgl_5674_0098.ppm >vgl_5674_0098.jpg
   real  0m0.109s
   user  0m0.029s
   sys   0m0.010s
 
 NOTE: {lib} can be lib, lib32, lib64, or lib/64, depending on the O/S and
 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.
 
-The Windows distribution of the libjpeg-turbo SDK installs jpeg62.dll into
-c:\libjpeg-turbo\bin, and the PATH environment variable can be modified such
-that this directory is searched before any others that might contain
-jpeg62.dll.  However, if jpeg62.dll also exists in an application's install
-directory, then Windows will load the application's version of it first.  Thus,
-if an application ships with jpeg62.dll, then back up the application's version
-of jpeg62.dll and copy c:\libjpeg-turbo\bin\jpeg62.dll into the application's
-install directory to accelerate it.
+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[64]\bin\jpeg*.dll into the
+application's install directory to accelerate it.
 
-The version of jpeg62.dll distributed in the libjpeg-turbo SDK requires the
-Visual C++ 2008 C run time DLL (msvcr90.dll).  This library ships with more
-recent versions of Windows, but users of older versions can obtain it from the
-Visual C++ 2008 Redistributable Package, which is available as a free download
-from Microsoft's web site.
+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 distributed version of jpeg62.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 libjpeg.62.dylib inside
+Mac applications typically embed their own copies of the libjpeg dylib inside
 the (hidden) application bundle, so it is not possible to globally replace
 libjpeg on OS X systems.  If an application uses a shared library version of
 libjpeg, then it may be possible to replace the application's version of it.
-This would generally involve copying libjpeg.62.dylib into the appropriate
-place in the application bundle and using install_name_tool to repoint the
-dylib to the new directory.  This requires an advanced knowledge of OS X and
-would not survive an upgrade or a re-install of the application.  Thus, it is
-not recommended for most users.
+This would generally involve copying libjpeg.*.dylib from libjpeg-turbo into
+the appropriate place in the application bundle and using install_name_tool to
+repoint the dylib to the new directory.  This requires an advanced knowledge of
+OS X and would not survive an upgrade or a re-install of the application.
+Thus, it is not recommended for most users.
 
 =======================
 Replacing TurboJPEG/IPP
 =======================
 
 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
 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.
 
 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.
 
 ========================================
 Using libjpeg-turbo in Your Own Programs
 ========================================
 
 For the most part, libjpeg-turbo should work identically to libjpeg, so in
 most cases, an application can be built against libjpeg and then run against
-libjpeg-turbo.  On Unix systems, you can build against libjpeg-turbo instead
-of libjpeg by setting
+libjpeg-turbo.  On Unix systems (including Cygwin), you can build against
+libjpeg-turbo instead of libjpeg by setting
 
   CPATH=/opt/libjpeg-turbo/include
   and
   LIBRARY_PATH=/opt/libjpeg-turbo/{lib}
 
 ({lib} = lib32 or lib64, depending on whether you are building a 32-bit or a
 64-bit application.)
 
-If using Cygwin, then set
-
-  CPATH=/cygdrive/c/libjpeg-turbo-gcc[64]/include
-  and
-  LIBRARY_PATH=/cygdrive/c/libjpeg-turbo-gcc[64]/lib
-
 If using MinGW, then set
 
   CPATH=/c/libjpeg-turbo-gcc[64]/include
   and
   LIBRARY_PATH=/c/libjpeg-turbo-gcc[64]/lib
 
 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
 version of libjpeg-turbo, you can use the following linker options:
 
   -Wl,-Bstatic -ljpeg -Wl,-Bdynamic
 
 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
-variable, and then link against either jpeg.lib (to use jpeg62.dll) or
-jpeg-static.lib (to use the static version of libjpeg-turbo.)
+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.)
 
 =====================
 Colorspace Extensions
 =====================
 
 libjpeg-turbo includes extensions which allow JPEG images to be compressed
-directly from (and decompressed directly to) buffers which use BGR, BGRA,
-RGBA, ABGR, and ARGB pixel ordering.  This is implemented with six new
+directly from (and decompressed directly to) buffers which use BGR, BGRX,
+RGBX, XBGR, and XRGB pixel ordering.  This is implemented with six new
 colorspace constants:
 
   JCS_EXT_RGB   /* red/green/blue */
   JCS_EXT_RGBX  /* red/green/blue/x */
   JCS_EXT_BGR   /* blue/green/red */
   JCS_EXT_BGRX  /* blue/green/red/x */
   JCS_EXT_XBGR  /* x/blue/green/red */
   JCS_EXT_XRGB  /* x/red/green/blue */
 
 Setting cinfo.in_color_space (compression) or cinfo.out_color_space
 (decompression) to one of these values will cause libjpeg-turbo to read the
 red, green, and blue values from (or write them to) the appropriate position in
 the pixel when YUV conversion is performed.
 
 Your application can check for the existence of these extensions at compile
 time with:
 
   #ifdef JCS_EXTENSIONS
 
 At run time, attempting to use these extensions with a version of libjpeg
 that doesn't support them will result in a "Bogus input colorspace" error.
+
+=================================
+libjpeg v7 and v8 API/ABI support
+=================================
+
+libjpeg v7 and v8 added new features to the API/ABI, and, unfortunately, the
+compression and decompression structures were extended in a backward-
+incompatible manner to accommodate these features.  Thus, programs which are
+built to use libjpeg v7 or v8 did not work with libjpeg-turbo, since it is
+based on the libjpeg v6b code base.  Although libjpeg v7 and v8 are still not
+as widely used as v6b, enough programs (including a few Linux distros) have
+made the switch that it was desirable to provide support for the libjpeg v7/v8
+API/ABI in libjpeg-turbo.
+
+Some of the libjpeg v7 and v8 features -- DCT scaling, to name one -- involve
+deep modifications to the code which cannot be accommodated by libjpeg-turbo
+without either breaking compatibility with libjpeg v6b or producing an
+unsupportable mess.  In order to fully support libjpeg v8 with all of its
+features, we would have to essentially port the SIMD extensions to the libjpeg
+v8 code base and maintain two separate code trees.  We are hesitant to do this
+until/unless the newer libjpeg code bases garner more community support and
+involvement and until/unless we have some notion of whether future libjpeg
+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 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.
+
+libjpeg v7 and v8 Features:
+---------------------------
+
+Fully supported:
+
+-- cjpeg: Separate quality settings for luminance and chrominance
+   Note that the libpjeg v7+ API was extended to accommodate this feature only
+   for convenience purposes.  It has always been possible to implement this
+   feature with libjpeg v6b (see rdswitch.c for an example.)
+
+-- cjpeg: 32-bit BMP support
+
+-- jpegtran: lossless cropping
+
+-- jpegtran: -perfect option
+
+-- rdjpgcom: -raw option
+
+-- rdjpgcom: locale awareness
+
+
+Fully supported when using libjpeg v7/v8 emulation:
+
+-- libjpeg: In-memory source and destination managers
+
+
+Not supported:
+
+-- libjpeg: DCT scaling in compressor
+   cinfo.scale_num and cinfo.scale_denom are silently ignored.
+
+-- libjpeg: IDCT scaling extensions in decompressor
+   libjpeg-turbo still supports IDCT scaling with scaling factors of 1/2, 1/4,
+   and 1/8 (same as libjpeg v6b.)
+
+-- libjpeg: Fancy downsampling in compressor
+   cinfo.do_fancy_downsampling is silently ignored.
+
+-- 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.