Update libjpeg-turbo to 1.2.

README-turbo.txt

 *******************************************************************************
 **     Background
 *******************************************************************************
 
-libjpeg-turbo is a derivative of libjpeg which 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
 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 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
@@ skipping 36 matching lines @@
 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
+libjpeg-turbo includes two APIs that 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
@@ skipping 42 matching lines @@
 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 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
+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
 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
 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.
@@ skipping 65 matching lines @@
 To build Visual C++ applications using libjpeg-turbo, add
 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, BGRX,
-RGBX, XBGR, and XRGB pixel ordering.  This is implemented with six new
+libjpeg-turbo includes extensions that allow JPEG images to be compressed
+directly from (and decompressed directly to) buffers that use BGR, BGRX,
+RGBX, XBGR, and XRGB pixel ordering.  This is implemented with ten 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 */
+  JCS_EXT_RGBA  /* red/green/blue/alpha */
+  JCS_EXT_BGRA  /* blue/green/red/alpha */
+  JCS_EXT_ABGR  /* alpha/blue/green/red */
+  JCS_EXT_ARGB  /* alpha/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.
+the pixel when compressing from/decompressing to an RGB buffer.
 
 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.
 
+When using the RGBX, BGRX, XBGR, and XRGB colorspaces during decompression, the
+X byte is undefined, and in order to ensure the best performance, libjpeg-turbo
+can set that byte to whatever value it wishes.  If an application expects the X
+byte to be used as an alpha channel, then it should specify JCS_EXT_RGBA,
+JCS_EXT_BGRA, JCS_EXT_ABGR, or JCS_EXT_ARGB.  When these colorspace constants
+are used, the X byte is guaranteed to be 0xFF, which is interpreted as opaque.
+
+Your application can check for the existence of the alpha channel colorspace
+extensions at compile time with:
+
+  #ifdef JCS_ALPHA_EXTENSIONS
+
+jcstest.c, located in the libjpeg-turbo source tree, demonstrates how to check
+for the existence of the colorspace extensions at compile time and run time.
+
 =================================
 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
+incompatible manner to accommodate these features.  Thus, programs that 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
+deep modifications to the code that 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
+of libjpeg-turbo that emulates the libjpeg v7 or v8 API/ABI, so that programs
+that 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
@@ skipping 51 matching lines @@
 ===============================================
 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.