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      1 TurboJPEG Java Wrapper
      2 ======================
      3 
      4 The TurboJPEG shared library can optionally be built with a Java Native
      5 Interface wrapper, which allows the library to be loaded and used directly from
      6 Java applications.  The Java front end for this is defined in several classes
      7 located under org/libjpegturbo/turbojpeg.  The source code for these Java
      8 classes is licensed under a BSD-style license, so the files can be incorporated
      9 directly into both open source and proprietary projects without restriction.  A
     10 Java archive (JAR) file containing these classes is also shipped with the
     11 "official" distribution packages of libjpeg-turbo.
     12 
     13 TJExample.java, which should also be located in the same directory as this
     14 README file, demonstrates how to use the TurboJPEG Java API to compress and
     15 decompress JPEG images in memory.
     16 
     17 
     18 Performance Pitfalls
     19 --------------------
     20 
     21 The TurboJPEG Java API defines several convenience methods that can allocate
     22 image buffers or instantiate classes to hold the result of compress,
     23 decompress, or transform operations.  However, if you use these methods, then
     24 be mindful of the amount of new data you are creating on the heap.  It may be
     25 necessary to manually invoke the garbage collector to prevent heap exhaustion
     26 or to prevent performance degradation.  Background garbage collection can kill
     27 performance, particularly in a multi-threaded environment (Java pauses all
     28 threads when the GC runs.)
     29 
     30 The TurboJPEG Java API always gives you the option of pre-allocating your own
     31 source and destination buffers, which allows you to re-use those buffers for
     32 compressing/decompressing multiple images.  If the image sequence you are
     33 compressing or decompressing consists of images of the same size, then
     34 pre-allocating the buffers is recommended.
     35 
     36 
     37 Installation Directory
     38 ----------------------
     39 
     40 The TurboJPEG Java Wrapper will look for the TurboJPEG JNI library
     41 (libturbojpeg.so, libturbojpeg.jnilib, or turbojpeg.dll) in the system library
     42 paths 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
     44 will look for the JNI library under the library directory configured when
     45 libjpeg-turbo was built.  If that library directory is
     46 /opt/libjpeg-turbo/lib32, then /opt/libjpeg-turbo/lib64 is also searched, and
     47 vice versa.
     48 
     49 If you installed the JNI library into another directory, then you will need
     50 to pass an argument of -Djava.library.path={path_to_JNI_library} to java, or
     51 manipulate LD_LIBRARY_PATH, DYLD_LIBRARY_PATH, or PATH to include the directory
     52 containing the JNI library.
     53