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author | dcommander <dcommander@3789f03b-4d11-0410-bbf8-ca57d06f2519> | 2012-02-07 00:15:42 +0000 |
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committer | dcommander <dcommander@3789f03b-4d11-0410-bbf8-ca57d06f2519> | 2012-02-07 00:15:42 +0000 |
commit | 553d8dac8238ae462e76c4441891a2dadcc0ee1b (patch) | |
tree | 1202ab97b60a7289855aa2c62055251e2dca99e9 /trunk | |
parent | 33ae69814c1de2a9e42cfb15cd50f5dc31fe607d (diff) |
Wordsmithing and grammar
git-svn-id: https://libjpeg-turbo.svn.sourceforge.net/svnroot/libjpeg-turbo@778 3789f03b-4d11-0410-bbf8-ca57d06f2519
Diffstat (limited to 'trunk')
-rwxr-xr-x | trunk/README-turbo.txt | 71 |
1 files changed, 36 insertions, 35 deletions
diff --git a/trunk/README-turbo.txt b/trunk/README-turbo.txt index 7c063fd..f452618 100755 --- a/trunk/README-turbo.txt +++ b/trunk/README-turbo.txt @@ -3,31 +3,31 @@ ******************************************************************************* 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 @@ -62,14 +62,14 @@ POSSIBILITY OF SUCH DAMAGE. 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 @@ -101,13 +101,13 @@ 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. +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 @@ -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. 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 @@ -146,7 +146,7 @@ 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 +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 @@ -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 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 @@ -342,12 +342,13 @@ 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. +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 |