Additional information/corrections involving libjpeg v7/v8b emulation

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DRC
2010-10-18 02:21:10 +00:00
parent 89c9085fcd
commit 7a4d1f0fdb

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@@ -75,36 +75,38 @@ 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 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
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
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 with the "official"
libjpeg-turbo SDK 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
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().
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
@@ -132,8 +134,8 @@ 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
@@ -142,12 +144,6 @@ of libjpeg by setting
({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
@@ -174,8 +170,8 @@ 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.)
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
@@ -229,11 +225,12 @@ 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, you can
build a version of libjpeg-turbo which emulates the libjpeg v7 or v8b 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.
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
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:
---------------------------