README
1TurboJPEG Java Wrapper
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3
4The TurboJPEG shared library can optionally be built with a Java Native
5Interface wrapper, which allows the library to be loaded and used directly from
6Java applications. The Java front end for this is defined in several classes
7located under org/libjpegturbo/turbojpeg. The source code for these Java
8classes is licensed under a BSD-style license, so the files can be incorporated
9directly into both open source and proprietary projects without restriction. A
10Java archive (JAR) file containing these classes is also shipped with the
11"official" distribution packages of libjpeg-turbo.
12
13TJExample.java, which should also be located in the same directory as this
14README file, demonstrates how to use the TurboJPEG Java API to compress and
15decompress JPEG images in memory.
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17
18Performance Pitfalls
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20
21The TurboJPEG Java API defines several convenience methods that can allocate
22image buffers or instantiate classes to hold the result of compress,
23decompress, or transform operations. However, if you use these methods, then
24be mindful of the amount of new data you are creating on the heap. It may be
25necessary to manually invoke the garbage collector to prevent heap exhaustion
26or to prevent performance degradation. Background garbage collection can kill
27performance, particularly in a multi-threaded environment (Java pauses all
28threads when the GC runs.)
29
30The TurboJPEG Java API always gives you the option of pre-allocating your own
31source and destination buffers, which allows you to re-use those buffers for
32compressing/decompressing multiple images. If the image sequence you are
33compressing or decompressing consists of images of the same size, then
34pre-allocating the buffers is recommended.
35
36
37Installation Directory
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39
40The TurboJPEG Java Wrapper will look for the TurboJPEG JNI library
41(libturbojpeg.so, libturbojpeg.jnilib, or turbojpeg.dll) in the system library
42paths or in any paths specified in LD_LIBRARY_PATH (Un*x), DYLD_LIBRARY_PATH
43(Mac), or PATH (Windows.) Failing this, on Un*x and Mac systems, the wrapper
44will look for the JNI library under the library directory configured when
45libjpeg-turbo was built. If that library directory is
46/opt/libjpeg-turbo/lib32, then /opt/libjpeg-turbo/lib64 is also searched, and
47vice versa.
48
49If you installed the JNI library into another directory, then you will need
50to pass an argument of -Djava.library.path={path_to_JNI_library} to java, or
51manipulate LD_LIBRARY_PATH, DYLD_LIBRARY_PATH, or PATH to include the directory
52containing the JNI library.
53