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- TurboJPEG Java Wrapper
- ======================
- The TurboJPEG shared library can optionally be built with a Java Native
- Interface wrapper, which allows the 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 Java API to compress and
- decompress JPEG images in memory.
- Performance Pitfalls
- --------------------
- The TurboJPEG Java API 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 TurboJPEG Java API always gives you the option of pre-allocating your own
- source and destination buffers, which allows you to re-use those 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.
- Installation Directory
- ----------------------
- The TurboJPEG Java Wrapper will look for the TurboJPEG JNI library
- (libturbojpeg.so, libturbojpeg.jnilib, or turbojpeg.dll) in the system library
- paths or in any paths specified in LD_LIBRARY_PATH (Un*x), DYLD_LIBRARY_PATH
- (Mac), or PATH (Windows.) Failing this, on Un*x and Mac systems, the wrapper
- will look for the JNI library under the library directory configured when
- libjpeg-turbo was built. If that library directory is
- /opt/libjpeg-turbo/lib32, then /opt/libjpeg-turbo/lib64 is also searched, and
- vice versa.
- If you installed the JNI library into another directory, then you will need
- to pass an argument of -Djava.library.path={path_to_JNI_library} to java, or
- manipulate LD_LIBRARY_PATH, DYLD_LIBRARY_PATH, or PATH to include the directory
- containing the JNI library.
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