TurboJPEG/OSS Java Wrapper
==========================

TurboJPEG/OSS can optionally be built with a Java Native Interface wrapper,
which allows the TurboJPEG/OSS dynamic library to be loaded and used directly
from Java applications.  The Java front end for this is defined in several
classes located under org/libjpegturbo/turbojpeg.  The source code for these
Java classes is licensed under a BSD-style license, so the files can be
incorporated directly into both open source and proprietary projects without
restriction.  A Java archive (JAR) file containing these classes is also
shipped with the "official" distribution packages of libjpeg-turbo.

TJExample.java, which should also be located in the same directory as this
README file, demonstrates how to use the TurboJPEG/OSS Java front end to
compress and decompress JPEG images in memory.


Performance Pitfalls
--------------------

The TurboJPEG Java front end defines several convenience methods that can
allocate image buffers or instantiate classes to hold the result of compress,
decompress, or transform operations.  However, if you use these methods, then
be mindful of the amount of new data you are creating on the heap.  It may be
necessary to manually invoke the garbage collector to prevent heap exhaustion
or to prevent performance degradation.  Background garbage collection can kill
performance, particularly in a multi-threaded environment (Java pauses all
threads when the GC runs.)

The Java front end always gives you the option of pre-allocating your own
source and destination buffers, which allows you to re-use these buffers for
compressing/decompressing multiple images.  If the image sequence you are
compressing or decompressing consists of images of the same size, then
pre-allocating the buffers is recommended.


Note for OS X users
-------------------

/usr/lib, the directory under which libturbojpeg.dylib is installed on Mac
systems, is not part of the normal Java library path.  Thus, when running a
Java application that uses TurboJPEG/OSS on Mac systems, you will need to pass
an argument of -Djava.library.path=/usr/lib to java.


Note for Solaris users
----------------------

/opt/libjpeg-turbo/lib, the directory under which libturbojpeg.so is installed
on Solaris systems, is not part of the normal Java library path.  Thus, when
running a Java application that uses TurboJPEG/OSS on Solaris systems, you will
need to pass an argument of -Djava.library.path=/opt/libjpeg-turbo/lib to java.
If using a 64-bit data model, then instead pass an argument of
-Djava.library.path=/opt/libjpeg-turbo/lib/amd64 to use the 64-bit version of
libturbojpeg.so.